HUD——1083 Courses

HUD——1083   Courses

Time Limit: 20000/10000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 7699    Accepted Submission(s):
3781

Problem Description

Consider a group of N students and P courses. Each
student visits zero, one or more than one courses. Your task is to determine
whether it is possible to form a committee of exactly P students that satisfies
simultaneously the conditions:

. every student in the committee
represents a different course (a student can represent a course if he/she visits
that course)

. each course has a representative in the
committee

Your program should read sets of data from a text file. The
first line of the input file contains the number of the data sets. Each data set
is presented in the following format:

P N
Count1 Student1 1 Student1 2
... Student1 Count1
Count2 Student2 1 Student2 2 ... Student2
Count2
......
CountP StudentP 1 StudentP 2 ... StudentP CountP

The
first line in each data set contains two positive integers separated by one
blank: P (1 <= P <= 100) - the number of courses and N (1 <= N <=
300) - the number of students. The next P lines describe in sequence of the
courses . from course 1 to course P, each line describing a course. The
description of course i is a line that starts with an integer Count i (0 <=
Count i <= N) representing the number of students visiting course i. Next,
after a blank, you'll find the Count i students, visiting the course, each two
consecutive separated by one blank. Students are numbered with the positive
integers from 1 to N.

There are no blank lines between consecutive sets
of data. Input data are correct.

The result of the program is on the
standard output. For each input data set the program prints on a single line
"YES" if it is possible to form a committee and "NO" otherwise. There should not
be any leading blanks at the start of the line.

An example of program
input and output:

 

Sample Input

2

3   3

3 1 2 3

2 1 2

1 1

3 3

2 1 3

2 1 3

1 1

 

Sample Output

YES

NO

Source

Southeastern
Europe 2000

 

题目大意：

需要选一个学生集合,这个集合满足:1.每个学生仅能代表一门学科  2.每门学科都需要一名学生来代表 ; 求是否存在这样的一个集合存在输出yes否则输出no

思路：

完美的一个模板题，判断一下最大匹配数是否等于课程数就ok了。

代码：

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<iostream>
#include<algorithm>
#define N 501
using namespace std;
bool vis[N];
int n,m,x,y,T,t,ans,pre[N],map[N][N];
int read()
{
    ,f=;char ch=getchar();
    ; ch=getchar();}
    +ch-'; ch=getchar();}
    return x*f;
}
int find(int x)
{
    ;i<=n;i++)
    {
        if(!vis[i]&&map[x][i])
        {
            vis[i]=true;
            ||find(pre[i]))
            {
                pre[i]=x;
                ;
            }
        }
    }
    ;
}
int main()
{
    T=read();
    while(T--)
    {
        ans=;
        memset(map,,sizeof(map));
        m=read(),n=read();
        ;i<=m;i++)
        {
            t=read();
            while(t--)
            {x=read();map[i][x]=;}
        }
        if(n<m) printf("NO\n");
        else
        {
            memset(pre,-,sizeof(pre));
            ;i<=m;i++)
            {
                memset(vis,,sizeof(vis));
                if(find(i)) ans++;
            }
        //    printf("%d\n",ans);
            if(ans==m) printf("YES\n");
            else printf("NO\n");
        }
    }
    ;
}