DNS records are cacheable only for their time to live (TTL). This limits query load, but it also means a changed authoritative answer does not instantly replace copies already held by resolvers.
Design a DnsTtlCache class:
DnsTtlCache() creates an empty cache.void store(String name, String value, int ttlSeconds, int now) stores or replaces a result.String resolve(String name, int now) returns the cached value or "MISS".
DNS names are case-insensitive, but stored values must be returned unchanged. A record stored at time t with TTL d is valid only while now < t + d. Resolving does not refresh its expiration. The value "NXDOMAIN" represents a negative DNS answer and follows the same TTL rules.
Calls on one object use nondecreasing now values.
Example 1:
Input:
Output:
Explanation: The expiration time is 100 + 10 = 110. The entry is valid at 109 and expired at 110.
Example 2:
Input:
Output:
Explanation: Case variants identify the same DNS name. Negative answers are cached to avoid repeatedly querying for a nonexistent name.
Constraints
1 <= name.length, value.length <= 255- Names contain only ASCII letters, digits, dots, and hyphens.
value != "MISS"0 <= ttlSeconds, now <= 10^9- Calls on one object have nondecreasing
now values. - At most
10^4 total method calls are made.
Implement a DNS TTL Cachemedium