题目要求:
力扣题解:
代码
import java.util.Arrays;
/**
* @program: mydemo
* @description: 力扣-数学-计数质数
* @author: Mr.zeng
* @create: 2021-02-22 09:47
**/
public class Solution33 {
public int countPrimes(int n){
int[] isPrime=new int[n];
Arrays.fill(isPrime,1);
int ans=0;
for (int i = 2; i < n; ++i) {
if(isPrime[i]==1){
ans+=1;
if((long)i*i<n){
for (int j = i*i; j < n; j+=i) {
isPrime[j]=0;
}
}
}
}
return ans;
}
}