POJ 1469 COURSES【二分图最大匹配】

分析：二分图最大匹配

代码：

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

const int maxn = 305;

int n;

vector<int> G[maxn];
int vis[maxn];
int Link[maxn];
bool Find(int u) {
    for(int i = 0;i < G[u].size(); i++) {
        int v = G[u][i];
        if(!vis[v]) {
            vis[v] = 1;
            if(Link[v] == -1 || Find(Link[v]) ) {
                Link[v] = u;
                return true;
            }
        }
    }
    return false;
}

int solve() {
    int cnt = 0;
    memset(Link, -1, sizeof(Link));
    for(int i = 1; i <= n; i++) {
        memset(vis, 0, sizeof(vis));
        if(Find(i)) cnt++;
    }
    return cnt;
}
int main() {
    int t;
    int p;
    int num, _num;
    scanf("%d",&t);
    while(t--) {
        scanf("%d %d",&n, &p);
        for(int i = 0; i <= n; i++) {
            G[i].clear();
        }
        for(int i = 1; i <= n; i++) {
            scanf("%d",&num);
            for(int j = 0; j < num; j++) {
                scanf("%d",&_num);
                G[i].push_back(_num);
            }
        }
        if(solve() == n) puts("YES");
        else puts("NO");
    }
    return 0;
}