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
kanna_3:
2019-03-24 04:44:33
HLD 0.22s
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ab_biswas09:
2019-03-19 22:11:46
NAIVE : 0.41
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mr_pandey:
2019-01-24 02:22:19
Take care of the queries where entry time of vertex v in euler path is less than that of vertex u
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amitnsky:
2019-01-05 17:48:02
Last edit: 2019-01-05 17:49:00 |
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jvjplus:
2018-12-27 08:53:41
naive: 0.36
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r_ash:
2018-10-30 12:40:37
take care when v and w are the same
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phoemur:
2018-10-09 22:42:24
Weak test cases. O(n) queries accepted |
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tanardi gunawan:
2018-10-03 13:40:07
AC IN ONE GO !!!! |
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cowshinafk:
2018-09-23 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: 2018-09-23 05:46:22 |
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himanshu pal:
2018-08-31 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. |
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 |