How should I practice Cousins in Binary Tree II?

Start by reading the full statement, solve the visible examples, then compare the pattern against related Amazon onsite interview problems in FastPrep.

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Problem · Tree

Cousins in Binary Tree II

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Problem statement

You are given a non-empty binary tree serialized as a level-order string array levelOrder. Each non-null token is a decimal integer, and "null" denotes a missing child.

Replace every node's value with the sum of the original values of all its cousins. Two nodes are cousins when they are at the same depth and have different parents. If a node has no cousins, its replacement value is 0.

All replacements are conceptually simultaneous. Return the updated tree using the same level-order array shape, preserving every "null" marker from the input.

Function

replaceValueInTree(levelOrder: String[]) → String[]

Examples

Example 1

levelOrder = ["5","4","9","1","10","null","7"]return = ["0","0","0","7","7","null","11"]

At depth 2, nodes 1 and 10 are siblings, so their only cousin has value 7. Node 7 has cousins with original values 1 and 10, whose sum is 11.

Example 2

levelOrder = ["3","1","2"]return = ["0","0","0"]

The root has no cousins, and the two nodes at depth 1 are siblings, so every replacement is 0.

Example 3

levelOrder = ["1","2","3","4","null","5","6"]return = ["0","0","0","11","null","4","4"]

At depth 2, node 4 receives 5 + 6 = 11, while sibling nodes 5 and 6 each receive the cousin value 4.