poj 1469

courses_1469.cpp

#include <cstdio>
#include <cstring>

#define NUM 501

int grid[NUM][NUM];
int used[NUM];
int path[NUM];

bool dfs(int x, int n)
{
    for(int i = 1; i <= n; i++)
    {
        if(used[i] == 0 && grid[x][i])
        {
            used[i] = 1;
            if(path[i] == 0 || dfs(path[i], n))//path[i] == 0 保证了第一条边和最后一条边为未匹配边
            {                                  //dfs(path[i], n)实现了交替路径
                path[i] = x;
                return true;
            }
        }
    }
    return false;
}

int match(int p, int s)
{
    memset(path, 0, sizeof(path));

    int sum = 0;
    for(int i = 1; i <= p; i++)
    {
        memset(used, 0, sizeof(used));
        if(dfs(i, s)) sum++;
    }
    return sum;
}
int main()
{
    int n;
    int p, s, sc;
    int st;
    scanf("%d", &n);
    while(n--)
    {
        scanf("%d%d", &p, &s);
        memset(grid, 0, sizeof(grid));
        for(int i = 1; i <= p; i++)
        {
            scanf("%d", &sc);
            for(int j = 1; j <= sc; j++)
            {
                scanf("%d", &st);
                grid[i][st] = 1;
            }
        }
        if(match(p, s) == p) printf("YES\n");
        else printf("NO\n");
    }
}