The K-th Distance
Time Limit: 8000/4000 MS (Java/Others) Memory Limit: 65536/65536 K (Java/Others)
Total Submission(s): 332 Accepted Submission(s): 90
Problem Description
Given a tree, which has n node in total. Define the distance between two node u and v is the number of edge on their unique route. So we can have n(n-1)/2 numbers for all the distance, then sort the numbers in ascending order. The task is to output the sum
of the first K numbers.
Input
There are several cases, first is the number of cases T. (There are most twenty cases).
For each case, the first line contain two integer n and K (2≤n≤100000,0≤K≤min(n(n?1)/2,106) ).
In following there are n-1 lines. Each line has two integer u , v. indicate that there is an edge between node u and v.
Output
For each case output the answer.
Sample Input
2 3 3 1 2 2 3 5 7 1 2 1 3 2 4 2 5
Sample Output
4 10
Source
题意：给出一棵树，边权为1，求前k长的路径和
思路：用一个队列维护即可，先将所有边入队，然后不停的用边的一个端点向外扩张，每扩张一次，路径长度就+1
这样求出前k个即可