# GitBook

Rikka with Graph

Time Limit: 2000/1000 MS (Java/Others)

Memory Limit: 65536/65536 K (Java/Others)

Problem Description

As we know, Rikka is poor at math. Yuta is worrying about this situation, so he gives Rikka some math tasks to practice. There is one of them:

Yuta has a non-direct graph with n vertices and n+1 edges. Rikka can choose some of the edges (at least one) and delete them from the graph.

Yuta wants to know the number of the ways to choose the edges in order to make the remaining graph connected.

It is too difficult for Rikka. Can you help her?

Input

The first line contains a number T(T≤30)——The number of the testcases.

For each testcase, the first line contains a number n(n≤100).

Then n+1 lines follow. Each line contains two numbers u,v , which means there is an edge between u and v.

Output

For each testcase, print a single number.

Sample Input

1
3
1 2
2 3
3 1
1 3

Sample Output

9

#include<stdio.h>
int par;
struct node {
int n,m;
} a;
int find(int m) {
if(m==par[m])
return m;
else
return par[m]=find(par[m]);
}
void unite(int x,int y) {
x=find(x);
y=find(y);
if(x==y)
return ;
else
par[y]=x;
}
int main() {
int T;
scanf("%d",&T);
while(T--) {
int n;
scanf("%d",&n);
for(int i=0; i<n+1; i++) {
scanf("%d %d",&a[i].n,&a[i].m);
}
int res=0;
for(int i=0; i<n+1; i++) {
for(int j=i; j<n+1; j++) {
for(int k=1; k<=n; k++)
par[k]=k;
for(int k=0; k<n+1; k++) {
if(k==i||k==j)
continue;
unite(a[k].n,a[k].m);
}
int k;
for(k=1; k<n; k++) {
if(find(n)!=find(k))
break;
}
if(k==n)
res++;
}
}
printf("%d\n",res);
}
return 0;
}