poj2594Treasure Exploration

因为点可以重复经过，所以要扩展边以把间接的变成直接的。。。。

/*****************************************
Author      :Crazy_AC(JamesQi)
Time        :2015
File Name   :
*****************************************/
// #pragma comment(linker, "/STACK:1024000000,1024000000")
#include <iostream>
#include <algorithm>
#include <iomanip>
#include <sstream>
#include <string>
#include <stack>
#include <queue>
#include <deque>
#include <vector>
#include <map>
#include <set>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <cstdlib>
#include <climits>
using namespace std;
#define MEM(x,y) memset(x, y,sizeof x)
#define pk push_back
typedef long long LL;
typedef unsigned long long ULL;
typedef pair<int,int> ii;
typedef pair<ii,int> iii;
const double eps = 1e-10;
const int inf = 1 << 30;
const int INF = 0x3f3f3f3f;
const int MOD = 1e9 + 7;
const int N = 510;
int g[N][N];
int linker[N];
bool vis[N];
int n, m;
bool dfs(int u) {
	for (int i = 1;i <= n;++i) {
		if (!vis[i] && g[u][i] && u != i) {
			vis[i] = true;
			if (linker[i] == -1 || dfs(linker[i])) {
				linker[i] = u;
				return true;
			}
		}
	}
	return false;
}
int hungary() {
	memset(linker, -1,sizeof linker);
	int ans = 0;
	for (int i = 1;i <= n;++i) {
		memset(vis,false,sizeof vis);
		if (dfs(i)) ans++;
	}
	return ans;
}
void floyd() {
	for (int k = 1;k <= n;++k) {
		for (int i = 1;i <= n;++i) {
			for (int j = 1;j <= n;++j)
				if (g[i][k] && g[k][j]) g[i][j] = 1;
		}
	}
}
int main()
{	
	// freopen("in.txt","r",stdin);
	// freopen("out.txt","w",stdout);
	while(scanf("%d%d",&n,&m) && (n + m)) {
		memset(g, 0,sizeof g);
		int u, v;
		for (int i = 1;i <= m;++i) {
			scanf("%d%d",&u,&v);
			g[u][v] = 1;
		}
		floyd();
		printf("%d\n", n - hungary());
	}
	return 0;
}