POJ 3041 Asteroids

#include <iostream>
#include <stdio.h>
#include <string.h>
#include <algorithm>
#include <cstdio>
using namespace std;

const int maxn = 550;
int N, K;
int mp[maxn][maxn];
int vis[maxn], match[maxn];

int path(int u) {
    for(int v = 1; v <= N; v ++) {
        if(mp[u][v] && !vis[v]) {
            vis[v] = 1;
            if(match[v] == -1 || path(match[v])) {
                match[v] = u;
                return 1;
            }
        }
    }
    return 0;
}

int main() {
    memset(mp, 0, sizeof(mp));
    memset(match, -1, sizeof(match));
    scanf("%d%d", &N, &K);

    for(int i = 0; i < K; i ++) {
        int x, y;
        scanf("%d%d", &x, &y);
        mp[x][y] = 1;
    }
    int cnt = 0;
    for(int i = 1; i <= N; i ++) {
        memset(vis, 0, sizeof(vis));
        if(path(i))
            cnt ++;
        else continue;
    }
    printf("%d\n", cnt);
    return 0;
}