TOJ-1317 Median Weight Bead

最新推荐文章于 2019-06-05 22:19:00 发布

转载最新推荐文章于 2019-06-05 22:19:00 发布 · 144 阅读

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原文链接：http://www.cnblogs.com/shenchuguimo/p/6349415.html

在一系列重量不同的珠子中，通过比较确定哪些珠子不可能是中位数重量，使用算法排除这些珠子，旨在找到可能成为中位数的珠子。

There are N beads which of the same shape and size, but with different weights. N is an odd number and the beads are labeled as 1, 2, ..., N. Your task is to find the bead whose weight is median (the ((N+1)/2)th among all beads). The following comparison has been performed on some pairs of beads:

A scale is given to compare the weights of beads. We can determine which one is heavier than the other between two beads. As the result, we now know that some beads are heavier than others. We are going to remove some beads which cannot have the medium weight.

For example, the following results show which bead is heavier after M comparisons where M=4 and N=5.

Bead 2 is heavier than Bead 1.
Bead 4 is heavier than Bead 3.
Bead 5 is heavier than Bead 1.
Bead 4 is heavier than Bead 2.

From the above results, though we cannot determine exactly which is the median bead, we know that Bead 1 and Bead 4 can never have the median weight: Beads 2, 4, 5 are heavier than Bead 1, and Beads 1, 2, 3 are lighter than Bead 4. Therefore, we can remove these two beads.

Write a program to count the number of beads which cannot have the median weight.

Input

The first line of the input file contains a single integer t (1 ≤ t ≤ 11), the number of test cases, followed by the input data for each test case. The input for each test case will be as follows:
The first line of input data contains an integer N (1 ≤ N ≤ 99) denoting the number of beads, and M denoting the number of pairs of beads compared. In each of the next M lines, two numbers are given where the first bead is heavier than the second bead.

Output

There should be one line per test case. Print the number of beads which can never have the medium weight.

Sample Input

Sample Output

Source: Tehran 2004 Iran Nationwide

#include <iostream>
#include <memory.h>
using namespace std;
int a[110][110];
int main(){
    int t,m,n,i,j,k,med,x,y,ans;
    cin>>t;
    while(t--){
        cin>>n>>m;
        memset(a,0,sizeof(a));
        med=(n+1)/2;
        ans=0;
        while(m--){
            cin>>x>>y;
            a[x][y]=1;
            a[y][x]=-1;
        }
        for(k=1;k<=n;k++){
            for(i=1;i<=n;i++){
                for(j=1;j<=n;j++){
                    if(a[i][k]>0 && a[k][j]>0)
                        a[i][j]=1;
                    if(a[i][k]<0 && a[k][j]<0)
                        a[i][j]=-1;
                }
            }
        }
        for(i=1;i<=n;i++){
            int s=0,b=0;
            for(j=1;j<=n;j++){
                if(a[i][j]>0)    b++;
                else if(a[i][j]<0)    s++;
            }
            if(b>=med)    ans++;
            else if(s>=med)    ans++;
        }
        cout<<ans<<endl;
    }
    return 0;
}

转载于:https://www.cnblogs.com/shenchuguimo/p/6349415.html