How should I practice Lowest Common Ancestor in a Parent Tree?

Start by reading the full statement, solve the visible examples, then compare the pattern against related BlackRock online assessment problems in FastPrep.

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Lowest Common Ancestor in a Parent Tree

BlackRock● EasyNEW GRADOA

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Problem statement

A rooted tree with nodes 0 through n - 1 is represented by parent. The root is node 0, parent[0] = -1, and for every other node i, parent[i] is its direct parent.

Given nodes p and q, return their lowest common ancestor: the common ancestor farthest from the root. A node is an ancestor of itself.

Function

lowestCommonAncestor(parent: int[], p: int, q: int) → int

Examples

Example 1

parent = [-1,0,0,1,1,2,2]p = 3q = 4return = 1

Nodes 3 and 4 are both direct children of node 1.

Example 2

parent = [-1,0,0,1,1,2,2]p = 3q = 6return = 0

The two nodes lie in different root subtrees.

Constraints

1 <= parent.length <= 100000.
parent[0] = -1.
For i > 0, 0 <= parent[i] < i.
0 <= p, q < parent.length.