LCA  Lowest Common Ancestor
A tree is an undirected graph in which any two vertices are connected by exactly one simple path. In other words, any connected graph without cycles is a tree.  Wikipedia
The lowest common ancestor (LCA) is a concept in graph theory and computer science. Let T be a rooted tree with N nodes. The lowest common ancestor is defined between two nodes v and w as the lowest node in T that has both v and w as descendants (where we allow a node to be a descendant of itself).  Wikipedia
Your task in this problem is to find the LCA of any two given nodes v and w in a given tree T.
For example the LCA of nodes 9 and 12 in this tree is the node number 3.
Input
The first line of input will be the number of test cases. Each test case will start with a number N the number of nodes in the tree, 1 <= N <= 1,000. Nodes are numbered from 1 to N. The next N lines each one will start with a number M the number of child nodes of the Nth node, 0 <= M <= 999 followed by M numbers the child nodes of the Nth node. The next line will be a number Q the number of queries you have to answer for the given tree T, 1 <= Q <= 1000. The next Q lines each one will have two number v and w in which you have to find the LCA of v and w in T, 1 <= v, w <= 1,000.
Input will guarantee that there is only one root and no cycles.
Output
For each test case print Q + 1 lines, The first line will have “Case C:” without quotes where C is the case number starting with 1. The next Q lines should be the LCA of the given v and w respectively.
Example
Input: 1 7 3 2 3 4 0 3 5 6 7 0 0 0 0 2 5 7 2 7 Output: Case 1: 3 1
hide comments
mr_pandey:
20190124 02:22:19
Take care of the queries where entry time of vertex v in euler path is less than that of vertex u


amitnsky:
20190105 17:48:02
Last edit: 20190105 17:49:00 

jvjplus:
20181227 08:53:41
naive: 0.36


r_ash:
20181030 12:40:37
take care when v and w are the same


phoemur:
20181009 22:42:24
Weak test cases. O(n) queries accepted 

tanardi gunawan:
20181003 13:40:07
AC IN ONE GO !!!! 

cowshinafk:
20180923 05:46:07
My first hit get WA 'cause i set all my array with the size of 1015, then i lift to 10015 and got AC. Last edit: 20180923 05:46:22 

himanshu pal:
20180831 05:01:06
Strange if I am using printf("%d\n", LCA(u, v)); Then it is giving me right answer and if I am using same code with no change but with cout << LCA(u,v) << endl; it gives me wrong answer Can anyone help me figure out what could be wrong here. 

aman_sachin200:
20180619 13:35:26
Did Using Euler Tour+RMQ!!! 

javier_dlg96:
20180414 00:44:12
For those with runtime errors, try setting maxN to something higher than what the problem states. 
Added by:  hossamyosef 
Date:  20130513 
Time limit:  0.600s1.113s 
Source limit:  50000B 
Memory limit:  1536MB 
Cluster:  Cube (Intel G860) 
Languages:  All 
Resource:  FCIS/ASU Local Contest 2013 