HDU 1083 Courses（ 匈牙利算法 ）

Courses

Time Limit: 20000/10000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 2915    Accepted Submission(s): 1368

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

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

 

Sample Output

YESNO 

 

题意：有p个课程和n个学生，每个学生可以自由选择课程（0到p个），现在要建立一个委员会，问是否能找到每个课程都有学生代表的集合，一个学生只能代表一个课程

import java.io.*;import java.util.*;public class Main {int t,p,n;int map[][]=new int[1000][3000];//记录选课情况int mark[]=new int[3000];//标记学生是否选课int link[]=new int[3000];//记录学生选的课public static void main(String[] args) {new Main().work();}void work(){Scanner sc=new Scanner(new BufferedInputStream(System.in));t=sc.nextInt();while(t--!=0){p=sc.nextInt();n=sc.nextInt();//初始化选课for(int i=1;i<=p;i++){Arrays.fill(map[i],0);int m=sc.nextInt();for(int j=1;j<=m;j++){int h=sc.nextInt();map[i][h]=1;}}int ans=0;Arrays.fill(link,0);for(int i=1;i<=p;i++){Arrays.fill(mark,0);if(DFS(i))ans++;}if(ans==p)System.out.println("YES");elseSystem.out.println("NO");}}boolean DFS(int x){for(int i=1;i<=n;i++){if(map[x][i]==1&&mark[i]==0){mark[i]=1;if((link[i]==0)||DFS(link[i])){link[i]=x;return true;}}}return false;}}