Binary search

#include <bits/stdc++.h>
using namespace std;

#define int long long

signed main()
{
    int n , q , x;
    cin >> n >> q;
    vector<int> a(n);
    for(int i = 0; i < n; i++){
        cin >> a[i];
    }
    while(q--){
        cin >> x;
        int l = 0 , r = n - 1;
        while(l < r){
            int mid = (l + r) / 2;
            if(a[mid] < x){
                l = mid + 1;
            }else{
                r = mid;
            }
        }
        //l == r
        cout << ((a[l] == x) ? "YES" : "NO") << endl;
    }
}