POJ - 1469 COURSES （匈牙利算法入门题）

#include <iostream>
#include <cstring>
#include <cstdio>
#include <vector>
using namespace std;
const int maxn = 1005;
int t; 
int k, s;
int flag;
int p, n;
int vis[maxn];
int match[maxn];
vector<int> g[maxn];
void init() {
    flag = 0;
    memset(match, -1, sizeof(match));
    for(int i = 1; i <= p+n; i++) g[i].clear();
}
bool dfs(int u) {
    vis[u] = 1;
    for(int i = 0; i < g[u].size(); i++) {
        int v = g[u][i], w = match[v];
        if(w<0 || !vis[w]&&dfs(w)) {
            match[u] = v;
            match[v] = u;
            return true;
        }
    }
    return false;
}
int hungarian() {
    int res = 0;
    for(int u = 1; u <= s+p; u++) {
        if(match[u] < 0) {
            memset(vis, 0, sizeof(vis));
            if(dfs(u)) res++;
        }
    }
    return res;
}
int main() {
    scanf("%d", &t);
    while(t--) {
        init();
        scanf("%d%d", &p, &n);
        for(int i = 1; i <= p; i++) {
            scanf("%d", &k);
            if(!k) flag = 1;
            while(k--) {
                scanf("%d", &s);
                g[i].push_back(s+p);
                g[s+p].push_back(i); 
            }
        }
        if(flag || n<p) {
            puts("NO");
            continue;
        }
        int ans = hungarian();
        if(ans == p) puts("YES");
        else puts("NO");
    }
}