[蓝书] POJ1741 点分治例题/[luogu] P4178/[GMOJ] 1166. Tree

相似题目：
https://www.luogu.com.cn/problem/P4178
https://www.luogu.com.cn/problem/P2634
https://www.luogu.com.cn/problem/P3806

Tree

Time Limit: 1000MS Memory Limit: 30M

Description

Give a tree with n vertices,each edge has a length(positive integer less than 1001).
Define dist(u,v)=The min distance between node u and v.
Give an integer k,for every pair (u,v) of vertices is called valid if and only if dist(u,v) not exceed k.
Write a program that will count how many pairs which are valid for a given tree.

$n(1\le n\le 10^4)$ 个点的树，每条边有边权 $w(1\le w\le 1000)$ 。
求所有的 $(x,y)$ 点对满足 $dist(x,y)\le k$ 的个数。

Input

The input contains several test cases. The first line of each test case contains two integers n, k. (n<=10000) The following n-1 lines each contains three integers u,v,l, which means there is an edge between node u and v of length l.
The last test case is followed by two zeros.

多组数据。对于每组数据，第一行输入 $n,k$ 。（如果 $n=k=0$ 则结束输入）。
接下来 $n-1$ 行，每行描述树上的一条双向边。

Output

For each test case output the answer on a single line.

对于每组数据，输出答案。

Sample Input

5 4
1 2 3
1 3 1
1 4 2
3 5 1
0 0

Sample Output

8

题解

https://blog.youkuaiyun.com/STJqwq/article/details/121263084

详解在这里。。。

一开始我想打洛谷 P3806 ，但是打不动了。。。被我盯上的序列乱搞题目都基本不放它过，嘿嘿嘿。