POJ 3041 Asteroids 题解

简单的二分图最大匹配

#include<iostream>
#include<vector> 
using namespace std;
#include<cstdio>
#include<cstring>

#define MAXN 510

int match[MAXN];
int map[MAXN][MAXN];
int vis[MAXN];
int K,M,N; 

int find(int x)
{
    for(int i=1;i<=N;i++)
    { 
        if(map[x][i]&&!vis[i])
        {
            vis[i] = 1;
            if(!match[i] || find(match[i]))
            {
                match[i] = x;
                return 1;
            }
        }
    }
    return 0;
} 

int main()
{
    while(scanf("%d%d",&N,&K)!=EOF)
    {
            memset(map,0,sizeof(map)); 
                memset(match,0,sizeof(match)); 
            int a,b;
            for(int i=0;i<K;i++)
            {
                scanf("%d%d",&a,&b);
                map[a][b]=1;    
            } 
            
            int ans=0;
            for(int i=1;i<=N;i++)
            {
                memset(vis,0,sizeof(vis));
                ans+=find(i);    
            } 
            printf("%d\n",ans);         
    } 
        return 0;    
}