HDU1068 Girls and Boys 最大独立子集

这题就是给定若干关系，求一个集合，该机和内部的各点之间没有任何关系，求得这个集合的元素最多为多少。

代码如下：

#include <cstdlib>
#include <cstring>
#include <cstdio>
#define MAXN 500
using namespace std;

int N, visit[MAXN], marry[MAXN], G[MAXN][MAXN];

int path(int u)
{
    for (int i = 0; i < N; ++i) {
        if (!G[u][i] || visit[i]) {
            continue;
        }
        visit[i] = 1;
        if (marry[i] == -1 || path(marry[i])) {
            marry[i] = u;
            return 1;
        }
    }
    return 0;
}

int main()
{
    int num, obj, a, ans;
    while (scanf("%d", &N) == 1) {
        ans = 0;
        memset(G, 0, sizeof (G));
        memset(marry, 0xff, sizeof (marry));
        for (int i = 0; i < N; ++i) {
            scanf("%d: (%d)", &a, &num);   
            for (int j = 0; j < num; ++j) {
                scanf("%d", &obj); 
                G[a][obj] = 1;
            }
        }
        for (int i = 0; i < N; ++i) {
            memset(visit, 0, sizeof (visit));
            if (path(i))
                ++ans;
        }
        printf("%d\n", N-(ans>>1));
    }
    return 0;
}