题目链接:http://poj.org/problem?id=2631 求树的直径模板. 定理: 树上任意一个点的在树上的最长路一定以树的直径的两端点其中一点结束. 做法: 两边bfs,第一次先找到node(树的直径的两端点其中一个),再一次求node的最长路所结束的点t node->t就是树的直径 #include <queue> #include <cstdio> #include <cstring> #include <iostream> #in…

http://poj.org/problem?id=2631 树的直径裸题 dfs/bfs均可 /* dfs */ #include <iostream> #include <cstdio> #include <algorithm> #include <cmath> #include <cstring> #include <string> using namespace std; ; #define yxy getchar() , p…

Roads in the North POJ - 2631 Building and maintaining roads among communities in the far North is an expensive business. With this in mind, the roads are build such that there is only one route from a village to a village that does not pass through…

题目连接 http://poj.org/problem?id=2631 Roads in the North Description Building and maintaining roads among communities in the far North is an expensive business. With this in mind, the roads are build such that there is only one route from a village to…

POJ 2631 Roads in the North(树的直径) http://poj.org/problem? id=2631 题意: 有一个树结构, 给你树的全部边(u,v,cost), 表示u和v两点间有一条距离为cost的边. 然后问你该树上最远的两个点的距离是多少?(即树的直径) 分析: 对于树的直径问题, <<算法导论>>(22 2-7)例题有说明. 详细解法: 首先从树上随意一个点a出发, (BFS)找出到这个点距离最远的点b. 然后在从b点出发(BFS)找到距离b…

Roads in the North Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 2359   Accepted: 1157 Description Building and maintaining roads among communities in the far North is an expensive business. With this in mind, the roads are build such…

Roads in the North Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 4513   Accepted: 2157 Description Building and maintaining roads among communities in the far North is an expensive business. With this in mind, the roads are build such…

地址 http://poj.org/problem?id=2431 题解 朴素想法就是dfs 经过该点的时候决定是否加油 中间加了一点剪枝 如果加油次数已经比已知最少的加油次数要大或者等于了 那么就剪枝 然而 还是TLE了 TLE代码 #include <iostream> #include <vector> #include <algorithm> #include <queue> using namespace std; vector<pair&l…

地址 http://poj.org/problem?id=1064 题解 二分即可 其实 对于输入与精度计算不是很在行 老是被卡精度 后来学习了一个函数 floor 向负无穷取整 才能ac 代码如下 #include <iostream> #include <vector> #include <math.h> #include <algorithm> using namespace std; vector<double> v; int n, k;…

Description Building and maintaining roads among communities in the far North is an expensive business. With this in mind, the roads are build such that there is only one route from a village to a village that does not pass through some other village…