题解

#include <bits/stdc++.h>
using namespace std;
int main() {
    int n ,m ,x;
    cin >> n >> m;
    int lst[n + 1] = {};
    for (int i = 1 ; i <= n ; i++)  //输入列表
        cin >> lst[i];
    for (int i = 1 ; i <= m ; i++){
        int l = 1 , r = n;
        bool f = 0;
        cin >> x;
        while (l <= r){  //二分法查找
            int mid = l + (r - l) / 2;
            if (lst[mid] == x){
                cout << mid << "\n";
                f = 1;
                break;
            }
            else if (lst[mid] < x)
                l = mid + 1;
            else
                r = mid - 1;
        }
        if (f == 0)
        	cout << -1 << "\n";
    }
    return 0;
}