3041.txt

北大ACM题目例程 详细的解答过程 程序实现 算法分析

Problem Id:3041  User Id:fzk 
#include <stdio.h>
#include <memory.h>
#define null 0
const int size = 510;
int maxmatch( int n, int m, bool w[][size], int *p)
{

	int p_n[size];
	int p_m[size];
	bool sign[size];
	int q[size],from[size],s,t;
	int i,j,link,now,h;
	memset( p_n, -1, sizeof(int)*n );
	memset( p_m, -1, sizeof(int)*m );
	for(i=0;i<n;i++)
	if(p_n[i]==-1)
	{
		memset( sign, 0, sizeof(bool)*m );             
		s=1;link=-1;
		from[0]=-1;
		q[0]=size-1;
		p_m[size-1]=i;
		for(t=0;t<s;t++)
		{
		   now=q[t];
		   for(j=0;j<m;j++)
		   {
			   if( w[p_m[now]][j] != null && sign[j]==0 )
			   {
					sign[j]=1;
					q[s]=j;
					from[s++]=t;
					if(p_m[j]==-1)
					{
						link=s-1;
						break;
					}
			   }
		   }
		   if(j<m)break;
		}
		if(t<s)
		{
			 while(from[link]!=-1)
			 {
					h=from[link];
					p_m[q[link]]=p_m[q[h]];
					p_n[p_m[q[h]]]=q[link];
					link=h;
			 }
		}
		//无完备匹配
		//else return 0;
	}
	int an;
	for(i=0,an=0;i<n;i++)
	{
		if(p)p[i]=p_n[i];
		if(p_n[i]>=0)an++;
	}
	return an;
}
bool map[510][510];
int main() {
	int n, k, i, a, b;
	scanf( "%d%d", &n, &k );
	for( i=0; i<k; i++ ) {
		scanf( "%d%d", &a, &b );
		a--, b--;
		map[a][b] = 1;
	}
	printf( "%d\n", maxmatch( n, n, map, 0 ) );
	return 0;
}