Description:

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

 

1 class Solution { 2 public: 3     int countPrimes(int n) { 4         vector
     
       num(n-1,true); 5         num[0]=false; 6         int res=0; 7         int limit=sqrt(n); 8  9         for(int i=2;i<=limit;i++)10         {11             if(num[i-1])12             {13                for(int j=i*i;j