Leetcode204-countPrimes

Posted on 2019-10-14 Edited on 2020-07-06 In leetcode Views: Valine:

Solution Report of LeetCode Acceptted

Description

Count the number of prime numbers less than a non-negative number, n.

Example

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

Solution

class Solution {
    public int countPrimes(int n) {
        boolean[] notPrimes = new boolean[n];
        int res =0;
        for (int i = 2; i < n; i++){
            if (notPrimes[i] == false){
                res ++;
                for (int j = 2; i * j < n; j++) notPrimes[i * j] = true; 
            }
        }
        return res;
    }
}