poj-3041-Asteroids

// poj 3041 hungary 

#include <cstdio>  
#include <cstring> 

const int MAXN = 500 + 10; 

int n, k, mp[MAXN][MAXN], vis[MAXN], match[MAXN]; 

bool dfs(int x){ 
	for(int i=1; i<=n; ++i){
		if( mp[x][i] != 0 && vis[i] == 0 ){
			vis[i] = 1; 
			if(match[i] < 0 || dfs(match[i])){
				match[i] = x;
				return true;  
			}
		}
	}
	return false; 
}

int main(){
	freopen("in.txt", "r", stdin); 

	int num, x, y; 
	while(scanf("%d %d", &n, &k) != EOF){
		memset(mp, 0, sizeof(mp)); 

		for(int i=0; i<k; ++i){
			scanf("%d %d", &x, &y);
			mp[x][y] = 1;  
		} 

		num = 0; 
		memset(match, -1, sizeof(match)); 

		for(int i=1; i<=n; ++i){ 
			memset(vis, 0, sizeof(vis)); 
			if( dfs( i ) ){
				++num; 
			} 
		} 
		printf("%d\n", num );
	}
	return 0; 
}