POJ 1469COURSES

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 
  

Input

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

P N 
Count1 Student_{1 1} Student_{1 2} ... Student_{1 Count1} 
Count2 Student_{2 1} Student_{2 2} ... Student_{2 Count2} 
... 
CountP Student_{P 1} Student_{P 2} ... Student_{P 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抣l 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. 

Output

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.

Sample Input

23 33 1 2 32 1 21 13 32 1 32 1 31 1

Sample Output

YES
NO

题目描述

n个学生去p个课堂，每一个学生都有自己的课堂，并且每个学生只能去一个课堂，题目要求能够安排每一个课堂都有人吗？

输入输出格式

输入格式：

第一行是测试数据的个数，

每组测试数据的开始分别是p和n，

接着p行，每行的开始是这个课堂的学生人数m，接着m个数代表该课堂的学生编号

输出格式：

如果该组数据能够这样安排就输出YES，否则输出NO。

输入输出样例

输入样例#1：

23 33 1 2 32 1 21 13 32 1 32 1 31 1

输出样例#1：

YESNO

说明

对于100%的数据，$n\le 100,m\le 300$

二分图最大匹配问题，匈牙利算法。

但莫名炸了一个点。。。

对拍了半小时，终于发现是 读入优化 的锅。。。

附代码：

#include<iostream>#include<algorithm>#include<cstdio>#include<cstring>#define MAXN 110#define MAXM 310using namespace std;int t,n,p,ans;int f[MAXM],a[MAXN][MAXM];bool vis[MAXM];bool find(int x){     for(int i=1;i<=n;i++){             if(!vis[i]&&a[x][i]){                                  vis[i]=true;                                  if(f[i]==-1||find(f[i])){                                                           f[i]=x;                                                           return true;                                                           }                                  }             }     return false;}int main(){    int x,y;    scanf("%d",&t);    while(t--){               memset(a,0,sizeof(a));               memset(f,-1,sizeof(f));               memset(vis,false,sizeof(vis));               scanf("%d%d",&p,&n);               if(p>n){                       printf("NO\n");                       continue;                       }               for(int i=1;i<=p;i++){                       scanf("%d",&x);                       for(int j=1;j<=x;j++){                               scanf("%d",&y);                               a[i][y]=1;                               }                       }               ans=0;               for(int i=1;i<=p;i++){                       memset(vis,false,sizeof(vis));                       if(find(i))                       ans++;                       }               if(ans==p)printf("YES\n");               else printf("NO\n");               }    return 0;}