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题目链接:
Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)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
2
3 2 1 2 10 3 1 15 1 2 2 32 2
1 2 100 1 2 2 1
Sample Output
10
25 100 100
Problem solving report:
Description: 在一个村庄里有n个地方,这n个地方每两个之间都有一条唯一的双向道。进行m次询问,A到B的距离是多少?
Problem solving: 利用vector,把每条路的起点当数组的下标,终点作为数组里面存的内容,然后把权值用另一个数组存一下(定义一个结构体),在深搜里面就把每个数组里面存的终点作为新的起点进入新的递归。直到找到终点。#include//动态数组的头文件#include #include #define N 40010using namespace std;struct edge { int v, w;};int vis[N], temp;vector a[N]; //定义一个结构体动态二维数组void DFS(int x, int y, int sum){ int i; if (x == y) { printf("%d\n", sum); temp = 1; return ; } int len = a[x].size(); //返回数组a[x]的元素个数 if (!len || vis[x] || temp) return ; for (int i = 0; i < len; i++) { vis[x] = 1; DFS(a[x][i].v, y, sum + a[x][i].w); vis[x] = 0; }}int main(){ int t, m, n, u, v, w, x, y; scanf("%d", &t); while (t--) { scanf("%d%d", &n, &m); memset(vis, 0, sizeof(vis)); for (int i = 0; i < n; i++) a[i].clear(); //清空动态数组 for (int i = 1; i < n; i++) { scanf("%d%d%d", &u, &v, &w); a[u].push_back((edge){v, w}); a[v].push_back((edge){u, w}); } for (int i = 0; i < m; i++) { temp = 0; scanf("%d%d", &x, &y); DFS(x, y, 0); } } return 0;}
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