1121 Damn Single （25 分）

#include<iostream>
#include<vector>
#include<set>
#include<cstring>
using namespace std;

int couple[100010];
int main()  
{
    int n, a, b, temp;
    memset(couple, -1, 100010);
    scanf("%d", &n);
    for (int i = 0; i < n; i++)
    {
        scanf("%d%d", &a, &b);
        couple[a] = b;
        couple[b] = a;
    }
    set<int> guest;
    scanf("%d", &n);
    for (int i = 0; i < n; i++)
    {
        scanf("%d", &temp);
        guest.insert(temp);
    }
    vector<int> ans;
    for (auto iter = guest.begin(); iter != guest.end(); iter++)
    {
        if (couple[*iter] == -1)
            ans.push_back(*iter);
        if (couple[*iter] != -1 && guest.find(couple[*iter]) == guest.end())
            ans.push_back(*iter);
    }
    printf("%d\n", ans.size());
    for (int i = 0; i < ans.size(); i++)
    {
        printf("%05d", ans[i]);
        if (i < ans.size() - 1) printf(" ");
    }
    system("pause");
    return 0;
}