思路

給N對(duì)夫妻編號(hào)，再給M個(gè)派對(duì)里的參與人的編號(hào)，輸出單身的人的編號(hào)（包括夫妻沒(méi)全部到場(chǎng)的也算單身）

代碼

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

unordered_map<int, int> couple;
int n, p;
vector<int> las;
int flag[100002];
vector<int> ans;

int main() {
    cin>>n;
    for (int i = 0; i < 2 * n; i++) {
        int num;
        cin>>num;
        couple[num] = i / 2 + 1;
    }
    cin>>p;
    for (int i = 0; i < p; i++) {
        int peo;
        cin>>peo;
        if (couple.find(peo) == couple.end()) {
            ans.push_back(peo);
        } else {
            las.push_back(peo);
            int n = couple[peo];
            flag[n]++;
        }
    }
    int t = las.size();
    for (int i = 0; i < t; i++) {
        int now = couple[las[i]];
        if (flag[now] == 1)
            ans.push_back(las[i]);
    }
    sort(ans.begin(), ans.end());
    int s = ans.size();
    cout<<s<<endl;
    for (int i = 0; i < s; i++) {
        printf("%05d", ans[i]);
        if (i != s - 1) cout<<" ";
        else cout<<endl;
    }
}