1121. Damn Single (25)

"Damn Single (单身狗)" is the Chinese nickname for someone who is being single. You are supposed to find those who are alone in a big party, so they can be taken care of.

Input Specification:

Each input file contains one test case. For each case, the first line gives a positive integer N (<=50000), the total number of couples. Then N lines of the couples follow, each gives a couple of ID's which are 5-digit numbers (i.e. from 00000 to 99999). After the list of couples, there is a positive integer M (<=10000) followed by M ID's of the party guests. The numbers are separated by spaces. It is guaranteed that nobody is having bigamous marriage (重婚) or dangling with more than one companion.

Output Specification:

First PRint in a line the total number of lonely guests. Then in the next line, print their ID's in increasing order. The numbers must be separated by exactly 1 space, and there must be no extra space at the end of the line.

311111 2222233333 4444455555 66666755555 44444 10000 88888 22222 11111 23333Sample Output:
510000 23333 44444 55555 88888
#include<cstdio>#include<set>#include<vector>#include<algorithm>using namespace std;const int maxn = 100000 + 10;int couple[maxn];int main(){	int N;	fill(couple, couple + maxn, -1);	scanf("%d", &N);	int a, b;	for (int i = 0; i < N; i++)	{		scanf("%d %d", &a, &b);		couple[a] = b;		couple[b] = a;	}	int M;	scanf("%d", &M);	set<int> single;	int t;	vector<int> v;	for (int i = 0; i < M; i++)	{		scanf("%d", &t);		v.push_back(t);	}	for (int i = 0; i < M; i++)	{		if (couple[v[i]] == -1)		{			single.insert(v[i]);		}		else		{						bool flag = false;			for (int j = 0; j < M; j++)			{				if (v[j] == couple[v[i]])				{					flag = true;					break;				}			}			if (!flag)			{				single.insert(v[i]);			}		}	}	printf("%d/n", single.size());	for (set<int>::iterator it = single.begin(); it != single.end(); it++)	{		if (it == single.begin())			printf("%05d", *it);		else			printf(" %05d", *it);	}	return 0;}