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
Mayank Ladia:
2015-07-08 16:43:23
Am getting SIGFPE error ? Can someone let me know why its so ? |
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xxbloodysantaxx:
2015-07-05 13:31:46
They should start writing "Print the case number " too. I am sick of getting WA due to that .... |
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sourabh:
2015-06-26 14:40:49
Has any one submitted by using spare table ?? |
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ftftfttfat:
2015-05-08 17:05:08
> is node 1 always a root?
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sai krishna:
2015-03-23 06:25:00
got AC with dp |
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Siddharth Singh:
2015-03-16 18:33:14
Runtime error , Really Don't Know whats wrong ,AC on LCASQ |
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Tushar Sinha:
2015-02-21 20:27:28
3 WA due to case :x |
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fanatique:
2015-01-24 13:40:02
is node 1 always a root? |
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AKASH GOEL:
2015-01-19 05:17:43
nice one
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Ayush Mishra:
2015-01-19 05:17:43
Ohh! It turns out that cin is slower than scanf. Scanf on the previous recursive code got accepted, whereas cin gives TLE |
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 |