Cousins in Binary Tree

The problem. Given the root of a binary tree with unique values, and two different values x and y, return true if their nodes are cousins: at the same depth, but with different parents.

Example

root = [1, 2, 3, null, 4, null, 5],  x = 5, y = 4   -> true
root = [1, 2, 3, 4, 5],              x = 4, y = 5   -> false   (siblings)
root = [1, 2, 3, 4],                 x = 4, y = 3   -> false   (different depths)

Two facts decide it: each node's depth and its parent. The approaches differ in how much they compute to get those two facts for just x and y.