LeetCode *** 204. Count Primes

class Solution {
public:
int countPrimes(int n) {
if(n==0||n==1||n==2)return 0;

int count=1,sq=sqrt(n);

bool *primes=new bool
;

for(int i=3;i<n;i+=2){
if(!primes[i]){
count++;
if(i<=sq){
for(int j=i<<1;j<n;j+=i)
primes[j]=true;
}
}
}

return count;
}
};