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
m_dodiya_072:
2022-09-06 15:44:54
clear the vector for new test case
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blrhyd0:
2022-08-21 21:21:04
where can i compare mem and time for my solution vs other for same problem in same lang(java) |
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shahid_92:
2022-01-25 08:27:57
using naive LCA 0.29sec
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fuadul_hasan:
2021-09-01 07:08:17
easy one |
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kryptonite28:
2021-07-25 14:49:25
input corresponding to the given diagram:
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yasser1110:
2021-07-23 12:25:44
Check this test case:-
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manito:
2021-06-30 08:47:52
why I am getting TLE in lca in binary lifting |
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tahoangquan2:
2021-03-28 08:38:18
output of the input below:
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sayskar:
2021-03-07 08:08:18
I am getting an RE .... anyone else also facing the same?? |
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hackerakhil:
2021-02-04 11:57:45
https://www.spoj.com/submit/LCA/id=27389011
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Added by: | hossamyosef |
Date: | 2013-05-13 |
Time limit: | 0.600s-1.113s |
Source limit: | 50000B |
Memory limit: | 1536MB |
Cluster: | Cube (Intel G860) |
Languages: | All |
Resource: | FCIS/ASU Local Contest 2013 |