A1121 Damn Single [水题]

#include<iostream>
#include<vector>
#include<map>
#include<string>
#include<cstring>
#include<cstdio>
#include<algorithm>
#include<set>
using namespace std;
map<int, int>m;
const int maxn = 10001;
int a[maxn];
set<int>sss;
int main()
{
	int n, temp1, temp2;
	cin >> n;
	for (int i = 0; i < n; i++)
	{
		cin >> temp1 >> temp2;
		m[temp1] = temp2;
		m[temp2] = temp1;
	}
	int j;
	cin >> j;
	for (int i = 0; i < j; i++)
	{
		cin >> a[i];
	}
	for (int i = 0; i < j; i++)
	{
		int *ans=find(a, a + j, m[a[i]]);
		if (ans == a + j)
		{
			sss.insert(a[i]);
		}
	}
	cout << sss.size() << endl;
	for (auto it = sss.begin(); it != sss.end(); it++)
	{
		if (it != sss.begin())
			cout << " ";
		printf("%05d", *it);
	}
	
}