{"title":"Exercise: Inheritance","description":null,"content":"Try implementing the below code exercises to reinforce your understanding. Your goal is to implement the classes below so that they produce the expected output.\n\n---\n\n# Exercise 1: Bank Account Hierarchy\n\n\n**Problem:** Build a bank account system using inheritance. The base `BankAccount` class has common fields and methods for deposits and withdrawals. Specialized account types have different withdrawal rules.\n\n**Requirements:**\n\n- Base `BankAccount` class with `ownerName`, `accountNumber`, and `balance` (protected). A `deposit(amount)` method that adds to the balance if the amount is positive. A `withdraw(amount)` method that subtracts from the balance if funds are sufficient and returns true/false. A `displayAccount()` method that prints the owner's name, account number, and formatted balance.\n- `SavingsAccount`: adds an `interestRate` field. Overrides `withdraw()` to enforce a minimum balance of $100 (the withdrawal fails if it would drop the balance below $100). Adds an `applyInterest()` method that increases the balance by `balance * interestRate / 100`.\n- `CheckingAccount`: adds an `overdraftLimit` field. Overrides `withdraw()` to allow withdrawals up to `balance + overdraftLimit`.\n- `displayAccount()` should work correctly for all account types without any changes to the base class.\n\n```java\nclass BankAccount {\n protected String ownerName;\n protected String accountNumber;\n protected double balance;\n\n public BankAccount(String ownerName, String accountNumber, double balance) {\n // TODO: initialize ownerName, accountNumber, and balance\n }\n\n public boolean deposit(double amount) {\n // TODO: add amount to balance if amount > 0, return true if successful\n return false;\n }\n\n public boolean withdraw(double amount) {\n // TODO: subtract amount from balance if balance >= amount, return true\n return false;\n }\n\n public void displayAccount() {\n // TODO: print \"ownerName (accountNumber) | Balance: $balance\"\n // Hint: use String.format(\"$%.2f\", balance) for formatting\n }\n}\n\nclass SavingsAccount extends BankAccount {\n private double interestRate;\n\n public SavingsAccount(String ownerName, String accountNumber,\n double balance, double interestRate) {\n super(ownerName, accountNumber, balance);\n // TODO: initialize interestRate\n }\n\n @Override\n public boolean withdraw(double amount) {\n // TODO: only allow if (balance - amount) >= 100 (minimum balance rule)\n return false;\n }\n\n public void applyInterest() {\n // TODO: add (balance * interestRate / 100) to balance\n }\n}\n\nclass CheckingAccount extends BankAccount {\n private double overdraftLimit;\n\n public CheckingAccount(String ownerName, String accountNumber,\n double balance, double overdraftLimit) {\n super(ownerName, accountNumber, balance);\n // TODO: initialize overdraftLimit\n }\n\n @Override\n public boolean withdraw(double amount) {\n // TODO: allow if (balance + overdraftLimit) >= amount\n return false;\n }\n}\n\npublic class Main {\n public static void main(String[] args) {\n SavingsAccount savings = new SavingsAccount(\"Alice\", \"SAV-001\", 1000, 2.0);\n savings.displayAccount();\n System.out.println(\"Withdraw $950: \" + savings.withdraw(950));\n savings.applyInterest();\n savings.displayAccount();\n\n System.out.println();\n\n CheckingAccount checking = new CheckingAccount(\"Bob\", \"CHK-002\", 500, 300);\n checking.displayAccount();\n System.out.println(\"Withdraw $700: \" + checking.withdraw(700));\n checking.displayAccount();\n }\n}\n```\n\n```python\nclass BankAccount:\n def __init__(self, owner_name: str, account_number: str, balance: float):\n # TODO: initialize self._owner_name, self._account_number, and self._balance\n pass\n\n def deposit(self, amount: float) -> bool:\n # TODO: add amount to balance if amount > 0, return True if successful\n return False\n\n def withdraw(self, amount: float) -> bool:\n # TODO: subtract amount from balance if balance >= amount, return True\n return False\n\n def display_account(self):\n # TODO: print \"owner_name (account_number) | Balance: $balance\"\n # Hint: use f\"${self._balance:.2f}\" for formatting\n pass\n\nclass SavingsAccount(BankAccount):\n def __init__(self, owner_name: str, account_number: str,\n balance: float, interest_rate: float):\n super().__init__(owner_name, account_number, balance)\n # TODO: initialize self._interest_rate\n\n def withdraw(self, amount: float) -> bool:\n # TODO: only allow if (balance - amount) >= 100\n return False\n\n def apply_interest(self):\n # TODO: add (balance * interest_rate / 100) to balance\n pass\n\nclass CheckingAccount(BankAccount):\n def __init__(self, owner_name: str, account_number: str,\n balance: float, overdraft_limit: float):\n super().__init__(owner_name, account_number, balance)\n # TODO: initialize self._overdraft_limit\n\n def withdraw(self, amount: float) -> bool:\n # TODO: allow if (balance + overdraft_limit) >= amount\n return False\n\nif __name__ == \"__main__\":\n savings = SavingsAccount(\"Alice\", \"SAV-001\", 1000, 2.0)\n savings.display_account()\n print(f\"Withdraw $950: {str(savings.withdraw(950)).lower()}\")\n savings.apply_interest()\n savings.display_account()\n\n print()\n\n checking = CheckingAccount(\"Bob\", \"CHK-002\", 500, 300)\n checking.display_account()\n print(f\"Withdraw $700: {str(checking.withdraw(700)).lower()}\")\n checking.display_account()\n```\n\n```cpp\n#include \n#include \n#include \n\nusing namespace std;\n\nclass BankAccount {\nprotected:\n string ownerName;\n string accountNumber;\n double balance;\n\npublic:\n BankAccount(const string& ownerName, const string& accountNumber,\n double balance) {\n // TODO: initialize this->ownerName, this->accountNumber, and this->balance\n }\n\n virtual ~BankAccount() {}\n\n bool deposit(double amount) {\n // TODO: add amount to balance if amount > 0, return true if successful\n return false;\n }\n\n virtual bool withdraw(double amount) {\n // TODO: subtract amount from balance if balance >= amount, return true\n return false;\n }\n\n void displayAccount() {\n // TODO: print \"ownerName (accountNumber) | Balance: $balance\"\n // Hint: use printf(\"$%.2f\", balance) for formatting\n }\n};\n\nclass SavingsAccount : public BankAccount {\nprivate:\n double interestRate;\n\npublic:\n SavingsAccount(const string& ownerName, const string& accountNumber,\n double balance, double interestRate)\n : BankAccount(ownerName, accountNumber, balance) {\n // TODO: initialize this->interestRate\n }\n\n bool withdraw(double amount) override {\n // TODO: only allow if (balance - amount) >= 100\n return false;\n }\n\n void applyInterest() {\n // TODO: add (balance * interestRate / 100) to balance\n }\n};\n\nclass CheckingAccount : public BankAccount {\nprivate:\n double overdraftLimit;\n\npublic:\n CheckingAccount(const string& ownerName, const string& accountNumber,\n double balance, double overdraftLimit)\n : BankAccount(ownerName, accountNumber, balance) {\n // TODO: initialize this->overdraftLimit\n }\n\n bool withdraw(double amount) override {\n // TODO: allow if (balance + overdraftLimit) >= amount\n return false;\n }\n};\n\nint main() {\n SavingsAccount savings(\"Alice\", \"SAV-001\", 1000, 2.0);\n savings.displayAccount();\n cout << \"Withdraw $950: \" << (savings.withdraw(950) ? \"true\" : \"false\") << endl;\n savings.applyInterest();\n savings.displayAccount();\n\n cout << endl;\n\n CheckingAccount checking(\"Bob\", \"CHK-002\", 500, 300);\n checking.displayAccount();\n cout << \"Withdraw $700: \" << (checking.withdraw(700) ? \"true\" : \"false\") << endl;\n checking.displayAccount();\n\n return 0;\n}\n```\n\n```go\npackage main\n\nimport \"fmt\"\n\ntype BankAccount struct {\n\townerName string\n\taccountNumber string\n\tbalance float64\n}\n\nfunc NewBankAccount(ownerName string, accountNumber string, balance float64) *BankAccount {\n\t// TODO: initialize ownerName, accountNumber, and balance\n\treturn &BankAccount{}\n}\n\nfunc (b *BankAccount) Deposit(amount float64) bool {\n\t// TODO: add amount to balance if amount > 0, return true if successful\n\treturn false\n}\n\nfunc (b *BankAccount) Withdraw(amount float64) bool {\n\t// TODO: subtract amount from balance if balance >= amount, return true\n\treturn false\n}\n\nfunc (b *BankAccount) DisplayAccount() {\n\t// TODO: print \"ownerName (accountNumber) | Balance: $balance\"\n\t// Hint: use fmt.Sprintf(\"$%.2f\", balance) for formatting\n\t_ = fmt.Sprintf(\"$%.2f\", b.balance)\n}\n\ntype SavingsAccount struct {\n\tBankAccount\n\tinterestRate float64\n}\n\nfunc NewSavingsAccount(ownerName string, accountNumber string, balance float64, interestRate float64) *SavingsAccount {\n\t// TODO: initialize interestRate\n\treturn &SavingsAccount{}\n}\n\nfunc (s *SavingsAccount) Withdraw(amount float64) bool {\n\t// TODO: only allow if (balance - amount) >= 100 (minimum balance rule)\n\treturn false\n}\n\nfunc (s *SavingsAccount) ApplyInterest() {\n\t// TODO: add (balance * interestRate / 100) to balance\n}\n\ntype CheckingAccount struct {\n\tBankAccount\n\toverdraftLimit float64\n}\n\nfunc NewCheckingAccount(ownerName string, accountNumber string, balance float64, overdraftLimit float64) *CheckingAccount {\n\t// TODO: initialize overdraftLimit\n\treturn &CheckingAccount{}\n}\n\nfunc (c *CheckingAccount) Withdraw(amount float64) bool {\n\t// TODO: allow if (balance + overdraftLimit) >= amount\n\treturn false\n}\n\nfunc main() {\n\tsavings := NewSavingsAccount(\"Alice\", \"SAV-001\", 1000, 2.0)\n\tsavings.DisplayAccount()\n\tfmt.Println(\"Withdraw $950:\", savings.Withdraw(950))\n\tsavings.ApplyInterest()\n\tsavings.DisplayAccount()\n\n\tfmt.Println()\n\n\tchecking := NewCheckingAccount(\"Bob\", \"CHK-002\", 500, 300)\n\tchecking.DisplayAccount()\n\tfmt.Println(\"Withdraw $700:\", checking.Withdraw(700))\n\tchecking.DisplayAccount()\n}\n```\n\n```csharp\nusing System;\n\npublic class BankAccount\n{\n protected string OwnerName;\n protected string AccountNumber;\n protected double Balance;\n\n public BankAccount(string ownerName, string accountNumber, double balance)\n {\n // TODO: initialize OwnerName, AccountNumber, and Balance\n }\n\n public bool Deposit(double amount)\n {\n // TODO: add amount to Balance if amount > 0, return true if successful\n return false;\n }\n\n public virtual bool Withdraw(double amount)\n {\n // TODO: subtract amount from Balance if Balance >= amount, return true\n return false;\n }\n\n public void DisplayAccount()\n {\n // TODO: print \"OwnerName (AccountNumber) | Balance: $Balance\"\n // Hint: use $\"{Balance:F2}\" for formatting\n }\n}\n\npublic class SavingsAccount : BankAccount\n{\n private double _interestRate;\n\n public SavingsAccount(string ownerName, string accountNumber,\n double balance, double interestRate)\n : base(ownerName, accountNumber, balance)\n {\n // TODO: initialize _interestRate\n }\n\n public override bool Withdraw(double amount)\n {\n // TODO: only allow if (Balance - amount) >= 100\n return false;\n }\n\n public void ApplyInterest()\n {\n // TODO: add (Balance * _interestRate / 100) to Balance\n }\n}\n\npublic class CheckingAccount : BankAccount\n{\n private double _overdraftLimit;\n\n public CheckingAccount(string ownerName, string accountNumber,\n double balance, double overdraftLimit)\n : base(ownerName, accountNumber, balance)\n {\n // TODO: initialize _overdraftLimit\n }\n\n public override bool Withdraw(double amount)\n {\n // TODO: allow if (Balance + _overdraftLimit) >= amount\n return false;\n }\n}\n\npublic class Program\n{\n public static void Main()\n {\n var savings = new SavingsAccount(\"Alice\", \"SAV-001\", 1000, 2.0);\n savings.DisplayAccount();\n Console.WriteLine(\"Withdraw $950: \" + savings.Withdraw(950).ToString().ToLower());\n savings.ApplyInterest();\n savings.DisplayAccount();\n\n Console.WriteLine();\n\n var checking = new CheckingAccount(\"Bob\", \"CHK-002\", 500, 300);\n checking.DisplayAccount();\n Console.WriteLine(\"Withdraw $700: \" + checking.Withdraw(700).ToString().ToLower());\n checking.DisplayAccount();\n }\n}\n```\n\n```typescript\nclass BankAccount {\n protected ownerName: string;\n protected accountNumber: string;\n protected balance: number;\n\n constructor(ownerName: string, accountNumber: string, balance: number) {\n // TODO: initialize using the constructor parameters\n this.ownerName = \"\";\n this.accountNumber = \"\";\n this.balance = 0;\n }\n\n deposit(amount: number): boolean {\n // TODO: add amount to balance if amount > 0, return true if successful\n return false;\n }\n\n withdraw(amount: number): boolean {\n // TODO: subtract amount from balance if balance >= amount, return true\n return false;\n }\n\n displayAccount(): void {\n // TODO: print \"ownerName (accountNumber) | Balance: $balance\"\n // Hint: use this.balance.toFixed(2) for formatting\n }\n}\n\nclass SavingsAccount extends BankAccount {\n private interestRate: number;\n\n constructor(ownerName: string, accountNumber: string,\n balance: number, interestRate: number) {\n super(ownerName, accountNumber, balance);\n // TODO: initialize this.interestRate using the parameter\n this.interestRate = 0;\n }\n\n withdraw(amount: number): boolean {\n // TODO: only allow if (balance - amount) >= 100\n return false;\n }\n\n applyInterest(): void {\n // TODO: add (balance * interestRate / 100) to balance\n }\n}\n\nclass CheckingAccount extends BankAccount {\n private overdraftLimit: number;\n\n constructor(ownerName: string, accountNumber: string,\n balance: number, overdraftLimit: number) {\n super(ownerName, accountNumber, balance);\n // TODO: initialize this.overdraftLimit using the parameter\n this.overdraftLimit = 0;\n }\n\n withdraw(amount: number): boolean {\n // TODO: allow if (balance + overdraftLimit) >= amount\n return false;\n }\n}\n\nconst savings = new SavingsAccount(\"Alice\", \"SAV-001\", 1000, 2.0);\nsavings.displayAccount();\nconsole.log(\"Withdraw $950: \" + savings.withdraw(950));\nsavings.applyInterest();\nsavings.displayAccount();\n\nconsole.log();\n\nconst checking = new CheckingAccount(\"Bob\", \"CHK-002\", 500, 300);\nchecking.displayAccount();\nconsole.log(\"Withdraw $700: \" + checking.withdraw(700));\nchecking.displayAccount();\n```\n\n#### Solutions\n\n```java\nclass BankAccount {\n protected String ownerName;\n protected String accountNumber;\n protected double balance;\n\n public BankAccount(String ownerName, String accountNumber, double balance) {\n this.ownerName = ownerName;\n this.accountNumber = accountNumber;\n this.balance = balance;\n }\n\n public boolean deposit(double amount) {\n if (amount > 0) {\n balance += amount;\n return true;\n }\n return false;\n }\n\n public boolean withdraw(double amount) {\n if (amount > 0 && balance >= amount) {\n balance -= amount;\n return true;\n }\n return false;\n }\n\n public void displayAccount() {\n System.out.println(ownerName + \" (\" + accountNumber + \") | Balance: \"\n + String.format(\"$%.2f\", balance));\n }\n}\n\nclass SavingsAccount extends BankAccount {\n private double interestRate;\n\n public SavingsAccount(String ownerName, String accountNumber,\n double balance, double interestRate) {\n super(ownerName, accountNumber, balance);\n this.interestRate = interestRate;\n }\n\n @Override\n public boolean withdraw(double amount) {\n if (amount > 0 && (balance - amount) >= 100) {\n balance -= amount;\n return true;\n }\n return false;\n }\n\n public void applyInterest() {\n balance += balance * interestRate / 100;\n }\n}\n\nclass CheckingAccount extends BankAccount {\n private double overdraftLimit;\n\n public CheckingAccount(String ownerName, String accountNumber,\n double balance, double overdraftLimit) {\n super(ownerName, accountNumber, balance);\n this.overdraftLimit = overdraftLimit;\n }\n\n @Override\n public boolean withdraw(double amount) {\n if (amount > 0 && (balance + overdraftLimit) >= amount) {\n balance -= amount;\n return true;\n }\n return false;\n }\n}\n\npublic class Main {\n public static void main(String[] args) {\n SavingsAccount savings = new SavingsAccount(\"Alice\", \"SAV-001\", 1000, 2.0);\n savings.displayAccount();\n System.out.println(\"Withdraw $950: \" + savings.withdraw(950));\n savings.applyInterest();\n savings.displayAccount();\n\n System.out.println();\n\n CheckingAccount checking = new CheckingAccount(\"Bob\", \"CHK-002\", 500, 300);\n checking.displayAccount();\n System.out.println(\"Withdraw $700: \" + checking.withdraw(700));\n checking.displayAccount();\n }\n}\n```\n\n```python\nclass BankAccount:\n def __init__(self, owner_name: str, account_number: str, balance: float):\n self._owner_name = owner_name\n self._account_number = account_number\n self._balance = balance\n\n def deposit(self, amount: float) -> bool:\n if amount > 0:\n self._balance += amount\n return True\n return False\n\n def withdraw(self, amount: float) -> bool:\n if amount > 0 and self._balance >= amount:\n self._balance -= amount\n return True\n return False\n\n def display_account(self):\n print(f\"{self._owner_name} ({self._account_number}) | Balance: ${self._balance:.2f}\")\n\nclass SavingsAccount(BankAccount):\n def __init__(self, owner_name: str, account_number: str,\n balance: float, interest_rate: float):\n super().__init__(owner_name, account_number, balance)\n self._interest_rate = interest_rate\n\n def withdraw(self, amount: float) -> bool:\n if amount > 0 and (self._balance - amount) >= 100:\n self._balance -= amount\n return True\n return False\n\n def apply_interest(self):\n self._balance += self._balance * self._interest_rate / 100\n\nclass CheckingAccount(BankAccount):\n def __init__(self, owner_name: str, account_number: str,\n balance: float, overdraft_limit: float):\n super().__init__(owner_name, account_number, balance)\n self._overdraft_limit = overdraft_limit\n\n def withdraw(self, amount: float) -> bool:\n if amount > 0 and (self._balance + self._overdraft_limit) >= amount:\n self._balance -= amount\n return True\n return False\n\nif __name__ == \"__main__\":\n savings = SavingsAccount(\"Alice\", \"SAV-001\", 1000, 2.0)\n savings.display_account()\n print(f\"Withdraw $950: {str(savings.withdraw(950)).lower()}\")\n savings.apply_interest()\n savings.display_account()\n\n print()\n\n checking = CheckingAccount(\"Bob\", \"CHK-002\", 500, 300)\n checking.display_account()\n print(f\"Withdraw $700: {str(checking.withdraw(700)).lower()}\")\n checking.display_account()\n```\n\n```cpp\n#include \n#include \n#include \n\nusing namespace std;\n\nclass BankAccount {\nprotected:\n string ownerName;\n string accountNumber;\n double balance;\n\npublic:\n BankAccount(const string& ownerName, const string& accountNumber,\n double balance)\n : ownerName(ownerName), accountNumber(accountNumber), balance(balance) {}\n\n virtual ~BankAccount() {}\n\n bool deposit(double amount) {\n if (amount > 0) {\n balance += amount;\n return true;\n }\n return false;\n }\n\n virtual bool withdraw(double amount) {\n if (amount > 0 && balance >= amount) {\n balance -= amount;\n return true;\n }\n return false;\n }\n\n void displayAccount() {\n char buf[32];\n sprintf(buf, \"$%.2f\", balance);\n cout << ownerName << \" (\" << accountNumber << \") | Balance: \"\n << buf << endl;\n }\n};\n\nclass SavingsAccount : public BankAccount {\nprivate:\n double interestRate;\n\npublic:\n SavingsAccount(const string& ownerName, const string& accountNumber,\n double balance, double interestRate)\n : BankAccount(ownerName, accountNumber, balance), interestRate(interestRate) {}\n\n bool withdraw(double amount) override {\n if (amount > 0 && (balance - amount) >= 100) {\n balance -= amount;\n return true;\n }\n return false;\n }\n\n void applyInterest() {\n balance += balance * interestRate / 100;\n }\n};\n\nclass CheckingAccount : public BankAccount {\nprivate:\n double overdraftLimit;\n\npublic:\n CheckingAccount(const string& ownerName, const string& accountNumber,\n double balance, double overdraftLimit)\n : BankAccount(ownerName, accountNumber, balance), overdraftLimit(overdraftLimit) {}\n\n bool withdraw(double amount) override {\n if (amount > 0 && (balance + overdraftLimit) >= amount) {\n balance -= amount;\n return true;\n }\n return false;\n }\n};\n\nint main() {\n SavingsAccount savings(\"Alice\", \"SAV-001\", 1000, 2.0);\n savings.displayAccount();\n cout << \"Withdraw $950: \" << (savings.withdraw(950) ? \"true\" : \"false\") << endl;\n savings.applyInterest();\n savings.displayAccount();\n\n cout << endl;\n\n CheckingAccount checking(\"Bob\", \"CHK-002\", 500, 300);\n checking.displayAccount();\n cout << \"Withdraw $700: \" << (checking.withdraw(700) ? \"true\" : \"false\") << endl;\n checking.displayAccount();\n\n return 0;\n}\n```\n\n```go\npackage main\n\nimport (\n\t\"fmt\"\n)\n\ntype BankAccount struct {\n\townerName string\n\taccountNumber string\n\tbalance float64\n}\n\nfunc NewBankAccount(ownerName, accountNumber string, balance float64) *BankAccount {\n\treturn &BankAccount{\n\t\townerName: ownerName,\n\t\taccountNumber: accountNumber,\n\t\tbalance: balance,\n\t}\n}\n\nfunc (b *BankAccount) Deposit(amount float64) bool {\n\tif amount > 0 {\n\t\tb.balance += amount\n\t\treturn true\n\t}\n\treturn false\n}\n\nfunc (b *BankAccount) Withdraw(amount float64) bool {\n\tif amount > 0 && b.balance >= amount {\n\t\tb.balance -= amount\n\t\treturn true\n\t}\n\treturn false\n}\n\nfunc (b *BankAccount) DisplayAccount() {\n\tfmt.Printf(\"%s (%s) | Balance: $%.2f\\n\", b.ownerName, b.accountNumber, b.balance)\n}\n\ntype SavingsAccount struct {\n\t*BankAccount\n\tinterestRate float64\n}\n\nfunc NewSavingsAccount(ownerName, accountNumber string, balance, interestRate float64) *SavingsAccount {\n\treturn &SavingsAccount{\n\t\tBankAccount: NewBankAccount(ownerName, accountNumber, balance),\n\t\tinterestRate: interestRate,\n\t}\n}\n\nfunc (s *SavingsAccount) Withdraw(amount float64) bool {\n\tif amount > 0 && (s.balance-amount) >= 100 {\n\t\ts.balance -= amount\n\t\treturn true\n\t}\n\treturn false\n}\n\nfunc (s *SavingsAccount) ApplyInterest() {\n\ts.balance += s.balance * s.interestRate / 100\n}\n\ntype CheckingAccount struct {\n\t*BankAccount\n\toverdraftLimit float64\n}\n\nfunc NewCheckingAccount(ownerName, accountNumber string, balance, overdraftLimit float64) *CheckingAccount {\n\treturn &CheckingAccount{\n\t\tBankAccount: NewBankAccount(ownerName, accountNumber, balance),\n\t\toverdraftLimit: overdraftLimit,\n\t}\n}\n\nfunc (c *CheckingAccount) Withdraw(amount float64) bool {\n\tif amount > 0 && (c.balance+c.overdraftLimit) >= amount {\n\t\tc.balance -= amount\n\t\treturn true\n\t}\n\treturn false\n}\n\nfunc main() {\n\tsavings := NewSavingsAccount(\"Alice\", \"SAV-001\", 1000, 2.0)\n\tsavings.DisplayAccount()\n\tfmt.Printf(\"Withdraw $950: %t\\n\", savings.Withdraw(950))\n\tsavings.ApplyInterest()\n\tsavings.DisplayAccount()\n\n\tfmt.Println()\n\n\tchecking := NewCheckingAccount(\"Bob\", \"CHK-002\", 500, 300)\n\tchecking.DisplayAccount()\n\tfmt.Printf(\"Withdraw $700: %t\\n\", checking.Withdraw(700))\n\tchecking.DisplayAccount()\n}\n```\n\n```csharp\nusing System;\n\npublic class BankAccount\n{\n protected string OwnerName;\n protected string AccountNumber;\n protected double Balance;\n\n public BankAccount(string ownerName, string accountNumber, double balance)\n {\n OwnerName = ownerName;\n AccountNumber = accountNumber;\n Balance = balance;\n }\n\n public bool Deposit(double amount)\n {\n if (amount > 0)\n {\n Balance += amount;\n return true;\n }\n return false;\n }\n\n public virtual bool Withdraw(double amount)\n {\n if (amount > 0 && Balance >= amount)\n {\n Balance -= amount;\n return true;\n }\n return false;\n }\n\n public void DisplayAccount()\n {\n Console.WriteLine($\"{OwnerName} ({AccountNumber}) | Balance: ${Balance:F2}\");\n }\n}\n\npublic class SavingsAccount : BankAccount\n{\n private double _interestRate;\n\n public SavingsAccount(string ownerName, string accountNumber,\n double balance, double interestRate)\n : base(ownerName, accountNumber, balance)\n {\n _interestRate = interestRate;\n }\n\n public override bool Withdraw(double amount)\n {\n if (amount > 0 && (Balance - amount) >= 100)\n {\n Balance -= amount;\n return true;\n }\n return false;\n }\n\n public void ApplyInterest()\n {\n Balance += Balance * _interestRate / 100;\n }\n}\n\npublic class CheckingAccount : BankAccount\n{\n private double _overdraftLimit;\n\n public CheckingAccount(string ownerName, string accountNumber,\n double balance, double overdraftLimit)\n : base(ownerName, accountNumber, balance)\n {\n _overdraftLimit = overdraftLimit;\n }\n\n public override bool Withdraw(double amount)\n {\n if (amount > 0 && (Balance + _overdraftLimit) >= amount)\n {\n Balance -= amount;\n return true;\n }\n return false;\n }\n}\n\npublic class Program\n{\n public static void Main()\n {\n var savings = new SavingsAccount(\"Alice\", \"SAV-001\", 1000, 2.0);\n savings.DisplayAccount();\n Console.WriteLine(\"Withdraw $950: \" + savings.Withdraw(950).ToString().ToLower());\n savings.ApplyInterest();\n savings.DisplayAccount();\n\n Console.WriteLine();\n\n var checking = new CheckingAccount(\"Bob\", \"CHK-002\", 500, 300);\n checking.DisplayAccount();\n Console.WriteLine(\"Withdraw $700: \" + checking.Withdraw(700).ToString().ToLower());\n checking.DisplayAccount();\n }\n}\n```\n\n```typescript\nclass BankAccount {\n protected ownerName: string;\n protected accountNumber: string;\n protected balance: number;\n\n constructor(ownerName: string, accountNumber: string, balance: number) {\n this.ownerName = ownerName;\n this.accountNumber = accountNumber;\n this.balance = balance;\n }\n\n deposit(amount: number): boolean {\n if (amount > 0) {\n this.balance += amount;\n return true;\n }\n return false;\n }\n\n withdraw(amount: number): boolean {\n if (amount > 0 && this.balance >= amount) {\n this.balance -= amount;\n return true;\n }\n return false;\n }\n\n displayAccount(): void {\n console.log(`${this.ownerName} (${this.accountNumber}) | Balance: $${this.balance.toFixed(2)}`);\n }\n}\n\nclass SavingsAccount extends BankAccount {\n private interestRate: number;\n\n constructor(ownerName: string, accountNumber: string,\n balance: number, interestRate: number) {\n super(ownerName, accountNumber, balance);\n this.interestRate = interestRate;\n }\n\n withdraw(amount: number): boolean {\n if (amount > 0 && (this.balance - amount) >= 100) {\n this.balance -= amount;\n return true;\n }\n return false;\n }\n\n applyInterest(): void {\n this.balance += this.balance * this.interestRate / 100;\n }\n}\n\nclass CheckingAccount extends BankAccount {\n private overdraftLimit: number;\n\n constructor(ownerName: string, accountNumber: string,\n balance: number, overdraftLimit: number) {\n super(ownerName, accountNumber, balance);\n this.overdraftLimit = overdraftLimit;\n }\n\n withdraw(amount: number): boolean {\n if (amount > 0 && (this.balance + this.overdraftLimit) >= amount) {\n this.balance -= amount;\n return true;\n }\n return false;\n }\n}\n\nconst savings = new SavingsAccount(\"Alice\", \"SAV-001\", 1000, 2.0);\nsavings.displayAccount();\nconsole.log(\"Withdraw $950: \" + savings.withdraw(950));\nsavings.applyInterest();\nsavings.displayAccount();\n\nconsole.log();\n\nconst checking = new CheckingAccount(\"Bob\", \"CHK-002\", 500, 300);\nchecking.displayAccount();\nconsole.log(\"Withdraw $700: \" + checking.withdraw(700));\nchecking.displayAccount();\n```\n\n\n---\n\n# Exercise 2: Shape Hierarchy\n\n\n**Problem:** Build a shape hierarchy where the base class provides a shared `describe()` method, and each child class implements its own `area()` and `perimeter()` methods.\n\n**Requirements:**\n\n- Base `Shape` class with a `name` field (protected). A `describe()` method that prints \"Shape: [name], Area: [area], Perimeter: [perimeter]\". Abstract-like `area()` and `perimeter()` methods that return 0 by default.\n- `Circle`: takes a `radius`. Area = pi *r^2, Perimeter = 2 *pi * r.\n- `Rectangle`: takes `width` and `height`. Area = w *h, Perimeter = 2 *(w + h).\n- `describe()` should work for any shape without modification because it calls `area()` and `perimeter()` internally.\n\n```java\nclass Shape {\n protected String name;\n\n public Shape(String name) {\n this.name = name;\n }\n\n public double area() {\n // TODO: return 0 by default\n return 0;\n }\n\n public double perimeter() {\n // TODO: return 0 by default\n return 0;\n }\n\n public void describe() {\n // TODO: print \"Shape: name, Area: area, Perimeter: perimeter\"\n // Hint: use String.format(\"%.2f\", value) for formatting\n }\n}\n\nclass Circle extends Shape {\n private double radius;\n\n public Circle(double radius) {\n super(\"Circle\");\n // TODO: initialize this.radius\n }\n\n @Override\n public double area() {\n // TODO: return Math.PI * radius * radius\n return 0;\n }\n\n @Override\n public double perimeter() {\n // TODO: return 2 * Math.PI * radius\n return 0;\n }\n}\n\nclass Rectangle extends Shape {\n private double width;\n private double height;\n\n public Rectangle(double width, double height) {\n super(\"Rectangle\");\n // TODO: initialize this.width and this.height\n }\n\n @Override\n public double area() {\n // TODO: return width * height\n return 0;\n }\n\n @Override\n public double perimeter() {\n // TODO: return 2 * (width + height)\n return 0;\n }\n}\n\npublic class Main {\n public static void main(String[] args) {\n Circle circle = new Circle(5.0);\n circle.describe();\n\n Rectangle rect = new Rectangle(4.0, 6.0);\n rect.describe();\n }\n}\n```\n\n```python\nimport math\n\nclass Shape:\n def __init__(self, name: str):\n self._name = name\n\n def area(self) -> float:\n # TODO: return 0 by default\n return 0\n\n def perimeter(self) -> float:\n # TODO: return 0 by default\n return 0\n\n def describe(self):\n # TODO: print \"Shape: name, Area: area, Perimeter: perimeter\"\n # Hint: use f\"{value:.2f}\" for formatting\n pass\n\nclass Circle(Shape):\n def __init__(self, radius: float):\n super().__init__(\"Circle\")\n # TODO: initialize self._radius\n\n def area(self) -> float:\n # TODO: return math.pi * radius * radius\n return 0\n\n def perimeter(self) -> float:\n # TODO: return 2 * math.pi * radius\n return 0\n\nclass Rectangle(Shape):\n def __init__(self, width: float, height: float):\n super().__init__(\"Rectangle\")\n # TODO: initialize self._width and self._height\n\n def area(self) -> float:\n # TODO: return width * height\n return 0\n\n def perimeter(self) -> float:\n # TODO: return 2 * (width + height)\n return 0\n\nif __name__ == \"__main__\":\n circle = Circle(5.0)\n circle.describe()\n\n rect = Rectangle(4.0, 6.0)\n rect.describe()\n```\n\n```cpp\n#include \n#include \n#include \n#include \n\nusing namespace std;\n\nclass Shape {\nprotected:\n string name;\n\npublic:\n Shape(const string& name) : name(name) {}\n virtual ~Shape() {}\n\n virtual double area() {\n // TODO: return 0 by default\n return 0;\n }\n\n virtual double perimeter() {\n // TODO: return 0 by default\n return 0;\n }\n\n void describe() {\n // TODO: print \"Shape: name, Area: area, Perimeter: perimeter\"\n // Hint: use printf(\"%.2f\", value) for formatting\n }\n};\n\nclass Circle : public Shape {\nprivate:\n double radius;\n\npublic:\n Circle(double radius) : Shape(\"Circle\") {\n // TODO: initialize this->radius\n }\n\n double area() override {\n // TODO: return M_PI * radius * radius\n return 0;\n }\n\n double perimeter() override {\n // TODO: return 2 * M_PI * radius\n return 0;\n }\n};\n\nclass Rectangle : public Shape {\nprivate:\n double width;\n double height;\n\npublic:\n Rectangle(double width, double height) : Shape(\"Rectangle\") {\n // TODO: initialize this->width and this->height\n }\n\n double area() override {\n // TODO: return width * height\n return 0;\n }\n\n double perimeter() override {\n // TODO: return 2 * (width + height)\n return 0;\n }\n};\n\nint main() {\n Circle circle(5.0);\n circle.describe();\n\n Rectangle rect(4.0, 6.0);\n rect.describe();\n\n return 0;\n}\n```\n\n```go\npackage main\n\nimport \"fmt\"\n\ntype Shape struct {\n\tname string\n}\n\nfunc NewShape(name string) *Shape {\n\treturn &Shape{name: name}\n}\n\nfunc (s *Shape) Area() float64 {\n\t// TODO: return 0 by default\n\treturn 0\n}\n\nfunc (s *Shape) Perimeter() float64 {\n\t// TODO: return 0 by default\n\treturn 0\n}\n\nfunc (s *Shape) Describe() {\n\t// TODO: print \"Shape: name, Area: area, Perimeter: perimeter\"\n\t// Hint: use fmt.Sprintf(\"%.2f\", value) for formatting\n\t_ = fmt.Sprintf(\"Shape: %s, Area: %.2f, Perimeter: %.2f\", s.name, s.Area(), s.Perimeter())\n}\n\ntype Circle struct {\n\tShape\n\tradius float64\n}\n\nfunc NewCircle(radius float64) *Circle {\n\tc := &Circle{\n\t\tShape: NewShape(\"Circle\"),\n\t}\n\t// TODO: initialize this.radius\n\treturn c\n}\n\nfunc (c *Circle) Area() float64 {\n\t// TODO: return math.Pi * radius * radius\n\treturn 0\n}\n\nfunc (c *Circle) Perimeter() float64 {\n\t// TODO: return 2 * math.Pi * radius\n\treturn 0\n}\n\ntype Rectangle struct {\n\tShape\n\twidth float64\n\theight float64\n}\n\nfunc NewRectangle(width float64, height float64) *Rectangle {\n\tr := &Rectangle{\n\t\tShape: NewShape(\"Rectangle\"),\n\t}\n\t// TODO: initialize this.width and this.height\n\treturn r\n}\n\nfunc (r *Rectangle) Area() float64 {\n\t// TODO: return width * height\n\treturn 0\n}\n\nfunc (r *Rectangle) Perimeter() float64 {\n\t// TODO: return 2 * (width + height)\n\treturn 0\n}\n\nfunc main() {\n\tcircle := NewCircle(5.0)\n\tcircle.Describe()\n\n\trect := NewRectangle(4.0, 6.0)\n\trect.Describe()\n}\n```\n\n```csharp\nusing System;\n\npublic class Shape\n{\n protected string Name;\n\n public Shape(string name) { Name = name; }\n\n public virtual double Area()\n {\n // TODO: return 0 by default\n return 0;\n }\n\n public virtual double Perimeter()\n {\n // TODO: return 0 by default\n return 0;\n }\n\n public void Describe()\n {\n // TODO: print \"Shape: Name, Area: area, Perimeter: perimeter\"\n // Hint: use $\"{value:F2}\" for formatting\n }\n}\n\npublic class Circle : Shape\n{\n private double _radius;\n\n public Circle(double radius) : base(\"Circle\")\n {\n // TODO: initialize _radius\n }\n\n public override double Area()\n {\n // TODO: return Math.PI * _radius * _radius\n return 0;\n }\n\n public override double Perimeter()\n {\n // TODO: return 2 * Math.PI * _radius\n return 0;\n }\n}\n\npublic class Rectangle : Shape\n{\n private double _width;\n private double _height;\n\n public Rectangle(double width, double height) : base(\"Rectangle\")\n {\n // TODO: initialize _width and _height\n }\n\n public override double Area()\n {\n // TODO: return _width * _height\n return 0;\n }\n\n public override double Perimeter()\n {\n // TODO: return 2 * (_width + _height)\n return 0;\n }\n}\n\npublic class Program\n{\n public static void Main()\n {\n var circle = new Circle(5.0);\n circle.Describe();\n\n var rect = new Rectangle(4.0, 6.0);\n rect.Describe();\n }\n}\n```\n\n```typescript\nclass Shape {\n protected name: string;\n\n constructor(name: string) {\n this.name = name;\n }\n\n area(): number {\n // TODO: return 0 by default\n return 0;\n }\n\n perimeter(): number {\n // TODO: return 0 by default\n return 0;\n }\n\n describe(): void {\n // TODO: print \"Shape: name, Area: area, Perimeter: perimeter\"\n // Hint: use value.toFixed(2) for formatting\n }\n}\n\nclass Circle extends Shape {\n private radius: number;\n\n constructor(radius: number) {\n super(\"Circle\");\n // TODO: initialize this.radius using the parameter\n this.radius = 0;\n }\n\n area(): number {\n // TODO: return Math.PI * radius * radius\n return 0;\n }\n\n perimeter(): number {\n // TODO: return 2 * Math.PI * radius\n return 0;\n }\n}\n\nclass Rectangle extends Shape {\n private width: number;\n private height: number;\n\n constructor(width: number, height: number) {\n super(\"Rectangle\");\n // TODO: initialize this.width and this.height using the parameters\n this.width = 0;\n this.height = 0;\n }\n\n area(): number {\n // TODO: return width * height\n return 0;\n }\n\n perimeter(): number {\n // TODO: return 2 * (width + height)\n return 0;\n }\n}\n\nconst circle = new Circle(5.0);\ncircle.describe();\n\nconst rect = new Rectangle(4.0, 6.0);\nrect.describe();\n```\n\n#### Solutions\n\n```java\nclass Shape {\n protected String name;\n\n public Shape(String name) {\n this.name = name;\n }\n\n public double area() {\n return 0;\n }\n\n public double perimeter() {\n return 0;\n }\n\n public void describe() {\n System.out.println(\"Shape: \" + name + \", Area: \"\n + String.format(\"%.2f\", area()) + \", Perimeter: \"\n + String.format(\"%.2f\", perimeter()));\n }\n}\n\nclass Circle extends Shape {\n private double radius;\n\n public Circle(double radius) {\n super(\"Circle\");\n this.radius = radius;\n }\n\n @Override\n public double area() {\n return Math.PI * radius * radius;\n }\n\n @Override\n public double perimeter() {\n return 2 * Math.PI * radius;\n }\n}\n\nclass Rectangle extends Shape {\n private double width;\n private double height;\n\n public Rectangle(double width, double height) {\n super(\"Rectangle\");\n this.width = width;\n this.height = height;\n }\n\n @Override\n public double area() {\n return width * height;\n }\n\n @Override\n public double perimeter() {\n return 2 * (width + height);\n }\n}\n\npublic class Main {\n public static void main(String[] args) {\n Circle circle = new Circle(5.0);\n circle.describe();\n\n Rectangle rect = new Rectangle(4.0, 6.0);\n rect.describe();\n }\n}\n```\n\n```python\nimport math\n\nclass Shape:\n def __init__(self, name: str):\n self._name = name\n\n def area(self) -> float:\n return 0\n\n def perimeter(self) -> float:\n return 0\n\n def describe(self):\n print(f\"Shape: {self._name}, Area: {self.area():.2f}, Perimeter: {self.perimeter():.2f}\")\n\nclass Circle(Shape):\n def __init__(self, radius: float):\n super().__init__(\"Circle\")\n self._radius = radius\n\n def area(self) -> float:\n return math.pi * self._radius * self._radius\n\n def perimeter(self) -> float:\n return 2 * math.pi * self._radius\n\nclass Rectangle(Shape):\n def __init__(self, width: float, height: float):\n super().__init__(\"Rectangle\")\n self._width = width\n self._height = height\n\n def area(self) -> float:\n return self._width * self._height\n\n def perimeter(self) -> float:\n return 2 * (self._width + self._height)\n\nif __name__ == \"__main__\":\n circle = Circle(5.0)\n circle.describe()\n\n rect = Rectangle(4.0, 6.0)\n rect.describe()\n```\n\n```cpp\n#include \n#include \n#include \n#include \n\nusing namespace std;\n\nclass Shape {\nprotected:\n string name;\n\npublic:\n Shape(const string& name) : name(name) {}\n virtual ~Shape() {}\n\n virtual double area() {\n return 0;\n }\n\n virtual double perimeter() {\n return 0;\n }\n\n void describe() {\n printf(\"Shape: %s, Area: %.2f, Perimeter: %.2f\\n\",\n name.c_str(), area(), perimeter());\n }\n};\n\nclass Circle : public Shape {\nprivate:\n double radius;\n\npublic:\n Circle(double radius) : Shape(\"Circle\"), radius(radius) {}\n\n double area() override {\n return M_PI * radius * radius;\n }\n\n double perimeter() override {\n return 2 * M_PI * radius;\n }\n};\n\nclass Rectangle : public Shape {\nprivate:\n double width;\n double height;\n\npublic:\n Rectangle(double width, double height)\n : Shape(\"Rectangle\"), width(width), height(height) {}\n\n double area() override {\n return width * height;\n }\n\n double perimeter() override {\n return 2 * (width + height);\n }\n};\n\nint main() {\n Circle circle(5.0);\n circle.describe();\n\n Rectangle rect(4.0, 6.0);\n rect.describe();\n\n return 0;\n}\n```\n\n```go\npackage main\n\nimport (\n\t\"fmt\"\n\t\"math\"\n)\n\ntype Shape struct {\n\tname string\n}\n\nfunc NewShape(name string) *Shape {\n\treturn &Shape{name: name}\n}\n\nfunc (s *Shape) Area() float64 {\n\treturn 0\n}\n\nfunc (s *Shape) Perimeter() float64 {\n\treturn 0\n}\n\nfunc (s *Shape) Describe() {\n\tfmt.Printf(\"Shape: %s, Area: %.2f, Perimeter: %.2f\\n\", s.name, s.Area(), s.Perimeter())\n}\n\ntype Circle struct {\n\t*Shape\n\tradius float64\n}\n\nfunc NewCircle(radius float64) *Circle {\n\treturn &Circle{\n\t\tShape: NewShape(\"Circle\"),\n\t\tradius: radius,\n\t}\n}\n\nfunc (c *Circle) Area() float64 {\n\treturn math.Pi * c.radius * c.radius\n}\n\nfunc (c *Circle) Perimeter() float64 {\n\treturn 2 * math.Pi * c.radius\n}\n\ntype Rectangle struct {\n\t*Shape\n\twidth float64\n\theight float64\n}\n\nfunc NewRectangle(width float64, height float64) *Rectangle {\n\treturn &Rectangle{\n\t\tShape: NewShape(\"Rectangle\"),\n\t\twidth: width,\n\t\theight: height,\n\t}\n}\n\nfunc (r *Rectangle) Area() float64 {\n\treturn r.width * r.height\n}\n\nfunc (r *Rectangle) Perimeter() float64 {\n\treturn 2 * (r.width + r.height)\n}\n\nfunc main() {\n\tcircle := NewCircle(5.0)\n\tcircle.Describe()\n\n\trect := NewRectangle(4.0, 6.0)\n\trect.Describe()\n}\n```\n\n```csharp\nusing System;\n\npublic class Shape\n{\n protected string Name;\n\n public Shape(string name) { Name = name; }\n\n public virtual double Area()\n {\n return 0;\n }\n\n public virtual double Perimeter()\n {\n return 0;\n }\n\n public void Describe()\n {\n Console.WriteLine($\"Shape: {Name}, Area: {Area():F2}, Perimeter: {Perimeter():F2}\");\n }\n}\n\npublic class Circle : Shape\n{\n private double _radius;\n\n public Circle(double radius) : base(\"Circle\")\n {\n _radius = radius;\n }\n\n public override double Area()\n {\n return Math.PI * _radius * _radius;\n }\n\n public override double Perimeter()\n {\n return 2 * Math.PI * _radius;\n }\n}\n\npublic class Rectangle : Shape\n{\n private double _width;\n private double _height;\n\n public Rectangle(double width, double height) : base(\"Rectangle\")\n {\n _width = width;\n _height = height;\n }\n\n public override double Area()\n {\n return _width * _height;\n }\n\n public override double Perimeter()\n {\n return 2 * (_width + _height);\n }\n}\n\npublic class Program\n{\n public static void Main()\n {\n var circle = new Circle(5.0);\n circle.Describe();\n\n var rect = new Rectangle(4.0, 6.0);\n rect.Describe();\n }\n}\n```\n\n```typescript\nclass Shape {\n protected name: string;\n\n constructor(name: string) {\n this.name = name;\n }\n\n area(): number {\n return 0;\n }\n\n perimeter(): number {\n return 0;\n }\n\n describe(): void {\n console.log(`Shape: ${this.name}, Area: ${this.area().toFixed(2)}, Perimeter: ${this.perimeter().toFixed(2)}`);\n }\n}\n\nclass Circle extends Shape {\n private radius: number;\n\n constructor(radius: number) {\n super(\"Circle\");\n this.radius = radius;\n }\n\n area(): number {\n return Math.PI * this.radius * this.radius;\n }\n\n perimeter(): number {\n return 2 * Math.PI * this.radius;\n }\n}\n\nclass Rectangle extends Shape {\n private width: number;\n private height: number;\n\n constructor(width: number, height: number) {\n super(\"Rectangle\");\n this.width = width;\n this.height = height;\n }\n\n area(): number {\n return this.width * this.height;\n }\n\n perimeter(): number {\n return 2 * (this.width + this.height);\n }\n}\n\nconst circle = new Circle(5.0);\ncircle.describe();\n\nconst rect = new Rectangle(4.0, 6.0);\nrect.describe();\n```\n","pageType":"lld-interviews"}

Exercise: Inheritance

Exercise 1: Bank Account Hierarchy

Exercise 2: Shape Hierarchy

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