How far away ？

Problem Description

There are n houses in the village and some bidirectional roads connecting them. Every day peole always like to ask like this "How far is it if I want to go from house A to house B"? Usually it hard to answer. But luckily int this village the answer is always unique, since the roads are built in the way that there is a unique simple path("simple" means you can't visit a place twice) between every two houses. Yout task is to answer all these curious people.

 

Input

First line is a single integer T(T<=10), indicating the number of test cases.
  For each test case,in the first line there are two numbers n(2<=n<=40000) and m (1<=m<=200),the number of houses and the number of queries. The following n-1 lines each consisting three numbers i,j,k, separated bu a single space, meaning that there is a road connecting house i and house j,with length k(0<k<=40000).The houses are labeled from 1 to n.
  Next m lines each has distinct integers i and j, you areato answer the distance between house i and house j.

 

Output

For each test case,output m lines. Each line represents the answer of the query. Output a bland line after each test case.

 

Sample Input

23 21 2 103 1 151 22 32 21 2 1001 22 1

 

Sample Output

1025100
100
题解：深搜做的，g++提交栈会爆，必须c++提交.
#include <iostream>#include <cstdio>#include <cstring>#include <vector>using namespace std;struct Node{int pos;int dis;};vector<Node> vec[40004];bool visited[40004];void dfs(int u,int v,int res){int k;visited[u] = true;     //访问过了 for(int i = 0;i < vec[u].size();i++){k = vec[u][i].pos;if(visited[k])       //已经访问 {continue;}if(v == k)       //找到目的地 {printf("%d\n",res + vec[u][i].dis);return;}else{dfs(k,v,res + vec[u][i].dis);}}}int main(){int ncase;cin>>ncase;int n,m;while(ncase--){scanf("%d%d",&n,&m);Node p,q;int u,v,d;for(int i = 1;i < n;i++){scanf("%d%d%d",&p.pos,&q.pos,&d);p.dis = q.dis = d;vec[p.pos].push_back(q);vec[q.pos].push_back(p);}for(int i = 0;i < m;i++){scanf("%d%d",&u,&v);memset(visited,false,sizeof(visited));dfs(u,v,0);}for(int i = 1;i <= n;i++){vec[i].clear();}}return 0;}