【題解】Codeforces 1435B. A New Technique

#include <bits/stdc++.h>
using namespace std;
 
int t, n, m, num, a[505][505];
 
int main(){
    cin >> t;
    while (t--){
        cin >> n >> m;
        map <int, int> mp;
        set <int> st;
        for (int i = 0; i < n; i++){
            for (int j = 0; j < m; j++){
                cin >> a[i][j];
            }
            st.insert(a[i][0]);
            mp[a[i][0]] = i;
        }
        for (int j = 0; j < m; j++){
            cin >> num;
            if (!st.count(num)){
                for (int i = 1; i < n; i++) cin >> num;
                continue;
            }
            for (int k = 0; k < m; k++){
                cout << a[mp[num]][k] << " ";
            }
            cout << "\n";
            for (int i = 1; i < n; i++){
                cin >> num;
                for (int k = 0; k < m; k++){
                    cout << a[mp[num]][k] << " ";
                }
                cout << "\n";
            }
        }
    }
}