Count Primes(LeetCode 204):

Problem

Given an integer n, return the number of prime numbers that are strictly less than n.

 

Example 1:

Input: n = 10
Output: 4
Explanation: There are 4 prime numbers less than 10, they are 2, 3, 5, 7.

Example 2:

Input: n = 0
Output: 0

Example 3:

Input: n = 1
Output: 0

 

Constraints:

  • 0 <= n <= 5 * 106