prime number in a range code example

Example: prime number in a range

//Prime Numbers & Sieve of Eratosthenes
#include <iostream>
#include<math.h>

using namespace std;
int count_prime(int n)
{
    bool bo[n+1];
    bo[0]=false;
    bo[1]=false;
    for(int i=2;i<=n;i++)
    {
        bo[i]=true;
    }
    int count=0;
    for(int i=2;i<=sqrt(n);i++)
    {
        for(int j=2*i;j<=n;j=j+i)
        {
            bo[j]=false;
        }
    }
    for(int i=2;i<=n;i++)
    {
        if(bo[i]==true)
        {
            count++;
        }
    }
    return count;
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    int t;
    cin>>t;
    while(t--)
    {
        int n;
        cin>>n;
        int ans=count_prime(n);
        cout<<ans<<endl;
    }
    return 0;
}