题目：P1571

测试点信息

代码（用的二分：

#include <bits/stdc++.h>
using namespace std;
int n, m;
int a[100001], b[100001];
int main(){
    cin >> n >> m;
    if (n == 0 || m == 0)
        return 0;
    for (int i = 0; i < n; i++) cin >> a[i];
    for (int i = 0; i < m; i++) cin >> b[i];
    sort(b, b + m);
    for (int i = 0; i < n; i++){
        int l = 0, r = n - 1;
        while(l <= r){
            int mid = (l + r) / 2;
            if (b[mid] == a[i]){
                cout << a[i] << " ";
                break;
            }
            if (b[mid] < a[i])
                l = mid + 1;
            else if (b[mid] > a[i])
                r = mid - 1;
        }
    }
}

求助QAQ