Girls and Boys

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点击打开链接

二分图匹配，hopcroft-karp

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>

using namespace std;

const int MAXN = 5010;
const int MAXM = 50010;

struct Edge{
	int to, next;
}edge[ MAXM ];

int head[ MAXN ], tot;

void init(){
	tot = 0;
	memset( head, -1, sizeof( head ) );
}

void addedge( int u, int v ){
	edge[ tot ].to = v;
	edge[ tot ].next = head[ u ];
	head[ u ] = tot++;
}

int linker[ MAXN ];
bool used[ MAXN ];
int uN;
bool dfs( int u ){
	for( int i = head[ u ]; i != -1; i = edge[ i ].next ){
		int v = edge[ i ].to;
		if( !used[ v ] ){
			used[ v ] = true;
			if( linker[ v ] == -1 || dfs( linker[ v ] ) ){
				linker[ v ] = u;
				return true;
			}
		}
	}
	return false;
}

int hungary(){
	int res = 0;
	memset( linker, -1, sizeof( linker ) );
	for( int u = 0; u < uN; ++u ){
		memset( used, false, sizeof( used ) );
		if( dfs( u ) ) 
			res++;
	}
	return res;
}

int main(){
	int n;
	while( scanf( "%d", &n ) != EOF ){
		init();
		int sum = 0;
		for( int i = 0;i < n; ++i ) {
			int temp1, temp2, temp;
			scanf( "%d: (%d)", &temp1, &temp2 );
			sum += temp2;
		//	cout << temp1 << " " << temp2 << endl;
			while( temp2-- ){
				scanf( "%d", &temp );
				addedge( temp1, temp );
			}
		}
		uN = n;
		int ans = hungary();
		cout << n - ans / 2 << endl;
	} 
	return 0;
}

Girls and Boys

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原文地址：http://blog.csdn.net/bo_jwolf/article/details/38149243