poj 3041 Asteroids

http://poj.org/problem?id=3041

 

 

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;
int map[510][510] = {0};
int match[510] = {0};
int value[510] = {0};
int n = 0;
int m = 0;
int x = 0;
int y = 0;
int find(int q)
{
    for(int i = 1;i <= n; ++i)
    {
        if(value[i] == 0 &&map[q][i])
        {
            value[i] = 1;
            if(match[i] == -1||find(match[i]))
            {
                match[i] = q;
                return 1;
            }
        }
    }
    return 0;
}
int main()
{
    while(~scanf("%d%d",&n,&m))
    {
        memset(map,0,sizeof(map));
        memset(match,-1,sizeof(match));
        for(int i = 1;i <= m;++i)
        {
            scanf("%d%d",&x,&y);
            map[x][y] = 1;
        }
        int ans = 0;
        for(int i = 1;i <= n;++i)
        {
            memset(value,0,sizeof(value));
        if(find(i))
        ++ans;
        }
        printf("%d\n",ans);
    }
    return 0;
}