使用二分查找或者map进行快速查找

使用map时间复杂度为O（m）

#include <iostream>
#include <map>
using namespace std;

int main() {
    int n;
    int m;
    while(cin>>n) {
        map<int,bool> mp;
        for (int i = 0; i < n; i++) {
            int temp;
            cin>>temp;
            mp[temp] = true;
        }
        cin>>m;
        for (int i = 0; i < m; i++) {
            int temp;
            cin>>temp;
            if (mp.find(temp) != mp.end()) {
                cout<<"YES"<<endl;
            } else {
                cout<<"NO"<<endl;
            }
        }
    }
}

使用二分查找时间复杂度为O(mlogn)

#include <iostream>
#include <algorithm>
using namespace std;

int main() {
    int n;
    int m;
    while(cin>>n) {
        int *arr = new int[n];
        for (int i = 0; i < n; i++) {
            cin>>arr[i];
        }
        sort(arr, arr+n);
        cin>>m;
        int *test = new int[m];
        for (int i = 0; i < m; i++) {
            cin>>test[i];
            if (binary_search(arr, arr + n, test[i])) {
                cout<<"YES"<<endl;
            } else {
                cout<<"NO"<<endl;
            }
        }
    }
}