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DSA
HardArray

Tree of Coprimes

arraymathtree

Problem Statement

There is a tree (i.e., a connected, undirected graph that has no cycles) consisting of n nodes numbered from 0 to n - 1 and exactly n - 1 edges. Each node has a value associated with it, and the root of the tree is node 0 .

To represent this tree, you are given an integer array nums and a 2D array edges . Each nums[i] represents the i ^th node's value, and each edges[j] = [u _j , v _j ] represents an edge between nodes u _j and v _j in the tree.

Two values x and y are coprime if gcd(x, y) == 1 where gcd(x, y) is the greatest common divisor of x and y .

An ancestor of a node i is any other node on the shortest path from node i to the root . A node is not considered an ancestor of itself.

Return an array ans of size n , where ans[i] is the closest ancestor to node i such that nums[i] and nums[ans[i]] are coprime , or -1 if there is no such ancestor .

Examples

Example 1
Input: nums = [2,3,3,2], edges = [[0,1],[1,2],[1,3]]
Output: [-1,0,0,1]
In the above figure, each node's value is in parentheses. - Node 0 has no coprime ancestors. - Node 1 has only one ancestor, node 0. Their values are coprime (gcd(2,3) == 1). - Node 2 has two ancestors, nodes 1 and 0. Node 1's value is not coprime (gcd(3,3) == 3), but node 0's value is (gcd(2,3) == 1), so node 0 is the closest valid ancestor. - Node 3 has two ancestors, nodes 1 and 0. It is coprime with node 1 (gcd(3,2) == 1), so node 1 is its closest valid ancestor.
Example 2
Input: nums = [5,6,10,2,3,6,15], edges = [[0,1],[0,2],[1,3],[1,4],[2,5],[2,6]]
Output: [-1,0,-1,0,0,0,-1]

Constraints

nums.length == n
1 <= nums[i] <= 50
1 <= n <= 10 ^5
edges.length == n - 1
edges[j].length == 2
0 <= u _j , v _j < n
u _j != v _j
😤
Hard
Difficulty
Topic Info
ModuleDSA
CategoryArray
Sub-topicMath
Tags
arraymathtreedepth-first searchnumber theory
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