題目:Count the number of prime numbers less than a non-negative number, n.
代碼:
public class Solution {
public int countPrimes(int n) {
boolean [] a = new boolean[n];
int count = 0;
for(int i=2;i<n;i++){
if(a[i]==false){
count++;
}
for(int j = 2 ;i*j<n;j++){
a[i*j]=true;
}
}
return count ;
}
}