Cousins in Binary Tree

Description

In a binary tree, the root node is at depth 0, and children of each depth k node are at depth k+1.

Two nodes of a binary tree are cousins if they have the same depth, but have different parents.

We are given the root of a binary tree with unique values, and the values x and y of two different nodes in the tree.

Return true if and only if the nodes corresponding to the values x and y are cousins.

 

Example 1:

Input: root = [1,2,3,4], x = 4, y = 3
Output: false

Example 2:

Input: root = [1,2,3,null,4,null,5], x = 5, y = 4
Output: true

Example 3:

Input: root = [1,2,3,null,4], x = 2, y = 3
Output: false

 

Constraints:

• The number of nodes in the tree will be between 2 and 100.
• Each node has a unique integer value from 1 to 100.

Solution(javascript)

const isCousins = function (root, x, y) {
  let parentA = null
  let depthA = 0
  let nodeB = null
  let depthB = 0
  const aux = (node, depth = 0, prev) => {
    if (node) {
      aux(node.left, depth + 1, node)
      if (node.val === x) {
        parentA = prev
        depthA = depth
      }
      if (node.val === y) {
        nodeB = node
        depthB = depth
      }
      aux(node.right, depth + 1, node)
    }
  }
  aux(root)
  return (depthA === depthB) && parentA && (parentA.left !== nodeB) && (parentA.right !== nodeB)
}