Longest Path

4.2

10 votes
Algorithms, Depth First Search, Graphs, Medium
Problem

You are given a tree with \(N\) nodes and \(N-1\) edges and an integer \(K\). Each node has a label denoted by an integer, \(A_i\). Your task is to find the length of the longest path such that label of all the nodes in the path are divisible by \(K\).

Length of a path is the number of edges in that path.

 

Input Format:

First line contains two space separated integers, \(N\) and \(K\). Next line contains \(N\) space separated integers, \(i^{th}\) integer denotes the label of \(i^{th}\) node, \(A_i\). Next \(N-1\) lines contains two space separated integers each, \(U\) and \(V\) denoting that there is an edge between node \(U\) and node \(V\).

 

Output Format:

Print a single integer denoting the length of the longest path such that label of all the nodes in the path are divisible by \(K\).

 

Constraints:

\(1 \le N \le 10^5\)

\(1 \le K \le 10^5\)

\(1 \le A_i \le 10^5\)

\(1 \le U, V \le N\)

Sample Input
6 2
4 2 3 2 3 5
1 2
1 3
2 4
2 5
3 6
Sample Output
2
Time Limit: 1
Memory Limit: 256
Source Limit:
Explanation

Longest path will be 1->2->4.

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