hdu2463 USTC campus network--BFS & STL

原题链接： http://acm.hdu.edu.cn/showproblem.php?pid=2463

一：题意

给n个点，标号1到n，每两点有连线，现给出m对关系a b表示a b之间的连线删除，求最后1能连通的点还有多少个。

二：AC代码

#define _CRT_SECURE_NO_DEPRECATE 

#include<iostream>
#include<stdio.h>
#include<string.h>
#include<queue>
#include<algorithm>
using namespace std;

int n, m;
bool vis[10010];
int pre[10010];
vector<int> v[10010];

int solve()
{
	queue<int> Q;
	vis[1] = 1;
	Q.push(1);
	int ans = 0;

	while (!Q.empty())
	{
		int x = Q.front();
		Q.pop();

		for (int i = 0; i < v[x].size(); i++)
			pre[v[x][i]] = x;

		for (int i = 1; i <= n; i++)
		{
			if (!vis[i] && pre[i] != x)
			{
				vis[i] = 1;
				Q.push(i);
				ans++;
			}
		}
	}

	return ans;
}

int main()
{
	int cas = 1;
	int a, b;

	while (~scanf("%d%d", &n, &m) && (n || m))
	{
		for (int i = 1; i <= n; i++)
			v[i].clear();

		for (int i = 1; i <= m; i++)
		{
			scanf("%d%d", &a, &b);
			v[a].push_back(b);
			v[b].push_back(a);
		}

		memset(vis, 0, sizeof(vis));
		memset(pre, 0, sizeof(pre));

		printf("Case %d: %d\n", cas++, solve());
	}
	return 0;
}