Sat, 04 Sep 2010 10:16:00 GMT

COURSES

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 �K�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

Sample Output

YES
NO
题意�Q�给������E�数跟学生数�Q�以及课�E�对应的学生�?br>求是否存在让所有课�E�跟不同的学生对应�?br>
#include <stdio.h>
#include <stdlib.h>
#define maxn 310
int map[maxn][maxn], hash[maxn], pre[maxn], gn, gm;
//gn左边x的点敎ͼ�gm双���y的点�?nbsp;
//pre是右边节点连接x中的节点 
//hash是右边的节点有没有被讉K���q?nbsp;
void set()
{
    for (int i = 1; i <= gn; i++)
    {
        for (int j = 1; j <= gm; j++)
        {
            map[i][j] = 0;
        }
    }
    for (int j = 1; j <= gm; j++)
    {
        pre[j] = -1;
    }
}
int han(int u)
{
    for (int v = 1; v <= gm; v++)
    {
        if (hash[v] == 0 && map[u][v])//边存在且双����Ҏ��被访问过 
        {
            hash[v] = 1;
            if (pre[v] == -1 || han(pre[v]))//v�q�没有前�|�节�Ҏ��v的前�|�节点存在增�q��\ 
            {
                pre[v] = u;//讑֮�v的前�|�节�?nbsp;
                return 1;
            }
        }
    }
    return 0;
}
int main()
{
    int t, i, j, m, u, v, num;
    scanf("%d", &t);
    while (t--)
    {
        scanf("%d%d", &gn, &gm);
        set();
        for (i = 1; i <= gn; i++)
        {
            scanf("%d", &m);
            while (m--)
            {
                scanf("%d", &v);
                map[i][v] = 1;
            }
        }
        for (i = 1, num = 0; i <= gn; i++)
        {
            for (j = 1; j <= gm; j++)
            {
                hash[j] = 0;
            }
            if (han(i))
            {
                num++;
            }
        }
        if (num == gn)
        {
            printf("YES\n");
        }
        else
        {
            printf("NO\n");
        }
    }
    system("pause");
    return 0;
}

火碳�?/a> 2010-09-04 18:16 发表评论

欧美在线视频观看免费网站,欧美成人资源网,免费视频一区二区三区在线观看