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Count Primes
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Input
Example 1
Example 2
Medium
Large
Custom
n
=
10
numbers 0 … 9
Sieve of Eratosthenes: cross out every prime's multiples
numbers 0 … 9
Sieve of Eratosthenes: cross out every prime's multiples
numbers 0 … 9
primes: 0
0
1
2
3
4
5
6
7
8
9
assume every number is prime;
0
and
1
are not
numbers 0 … 9
primes: 1
0
1
2
3
4
5
6
7
8
9
2
is prime → cross out
2², 2²+2, …
numbers 0 … 9
primes: 1
0
1
2
3
4
5
6
7
8
9
cross out
4
= 2 × 2
numbers 0 … 9
primes: 1
0
1
2
3
4
5
6
7
8
9
cross out
6
= 2 × 3
numbers 0 … 9
primes: 1
0
1
2
3
4
5
6
7
8
9
all multiples of
2
are crossed out
numbers 0 … 9
primes: 1
0
1
2
3
4
5
6
7
8
9
3
is still uncrossed → it is prime
numbers 0 … 9
primes: 2
0
1
2
3
4
5
6
7
8
9
3
is prime → cross out
3², 3²+3, …
numbers 0 … 9
primes: 2
0
1
2
3
4
5
6
7
8
9
all multiples of
3
are crossed out
numbers 0 … 9
primes: 4
0
1
2
3
4
5
6
7
8
9
the survivors are the primes →
4 primes below 10
4 primes below 10
algo
master
.
io
Step:
Count the primes below 10
0 / 12
Input
Example 1
Example 2
Medium
Large
Custom
n
=
10
0 / 12
algo
master
.
io
Step:
Count the primes below 10
