Distance Queries（LCA+tarjan）-优快云博客

本文链接：https://blog.youkuaiyun.com/qq_43470233/article/details/98885950

Farmer John面临一个问题，他的奶牛拒绝参加马拉松比赛，因为路线太长。他希望找到一条更合理的路径。输入包括“Navigation Nightmare”问题的相同输入，后面跟着一个整数K，表示距离查询的数量。每个距离查询包含两个农场的编号，需要计算两者之间的路径距离。输出为每个查询的距离。样例输入和输出展示了具体的操作过程。

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Distance Queries

Farmer John’s cows refused to run in his marathon since he chose a path much too long for their leisurely lifestyle. He therefore wants to find a path of a more reasonable length. The input to this problem consists of the same input as in “Navigation Nightmare”,followed by a line containing a single integer K, followed by K “distance queries”. Each distance query is a line of input containing two integers, giving the numbers of two farms between which FJ is interested in computing distance (measured in the length of the roads along the path between the two farms). Please answer FJ’s distance queries as quickly as possible!
Input

Lines 1…1+M: Same format as “Navigation Nightmare”
Line 2+M: A single integer, K. 1 <= K <= 10,000
Lines 3+M…2+M+K: Each line corresponds to a distance query and contains the indices of two farms.
Output
Lines 1…K: For each distance query, output on a single line an integer giving the appropriate distance.
Sample Input
7 6
1 6 13 E
6 3 9 E
3 5 7 S
4 1 3 N
2 4 20 W
4 7 2 S
3
1 6
1 4
2 6
Sample Output
13
3
36
Hint
Farms 2 and 6 are 20+3+13=36 apart.

ac代码：

#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstring>
using namespace std;
const int MAXN = 80080;
const int MAXQ = 20020;
 
int father[MAXN],Head[MAXN],QHead[MAXN],Dist[MAXN];
 
struct EdgeNode
{
   
    int to;
    int next;
    int lca;
}Edges[MAXN];
 
EdgeNode QEdges[MAXN];
 
int find(int x)
{
   
    if(x != father[x])
        father[x] = find(father[x])