HDU 4916 树形dp

Count on the path

Time Limit: 5000/2500 MS (Java/Others)    Memory Limit: 131072/131072 K (Java/Others)
Total Submission(s): 92    Accepted Submission(s): 10

Problem Description

bobo has a tree, whose vertices are conveniently labeled by 1,2,…,n.

Let f(a,b) be the minimum of vertices not on the path between vertices a and b.

There are q queries (u _i,v _i) for the value of f(u _i,v _i). Help bobo answer them.

 

Input

The input consists of several tests. For each tests:

The first line contains 2 integers n,q (4≤n≤10 ⁶,1≤q≤10 ⁶). Each of the following (n - 1) lines contain 2 integers a _i,b _i denoting an edge between vertices a _i and b _i (1≤a _i,b _i≤n). Each of the following q lines contains 2 integer u′ _i,v′ _i (1≤u _i,v _i≤n).

The queries are encrypted in the following manner.

u ₁=u′ ₁,v ₁=v′ ₁.
For i≥2, u _i=u′ _i⊕f(u _{i - 1},v _{i - 1}),v _i=v′ _i⊕f(u _i-1,v _i-1).

Note ⊕ denotes bitwise exclusive-or.

It is guaranteed that f(a,b) is defined for all a,b.

The task contains huge inputs. `scanf` in g++ is considered too slow to get accepted. You may (1) submit the solution in c++; or (2) use hand-written input utilities.

 

Output

For each tests:

For each queries, a single number denotes the value.

 

Sample Input

  
    
    
    
    

     
     
     
     
   4 1
1 2
1 3
1 4
2 3
5 2
1 2
1 3
2 4
2 5
1 2
7 6
  
    
    
    
    

 

Sample Output

  
    
    
    
    

     
     
     
     
   4
3
1
  
    
    
    
    

 

Author

Xiaoxu Guo (ftiasch)

给定一棵树，求不经过路径的最小标号。

把1作为根，然后加入不经过1，那么答案直接为1，否则就是预处理，

数据规模很大，所以只能用bfs，并且需要加读写外挂，具体过程代码详解。

代码：

/* ***********************************************
Author :rabbit
Created Time :2014/8/6 10:44:17
File Name :5.cpp
************************************************ */
#pragma comment(linker, "/STACK:102400000,102400000")
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include