How should I practice Binary Tree Target-Sum Paths?

Start by reading the full statement, solve the visible examples, then compare the pattern against related ByteDance phone screen problems in FastPrep.

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Problem · Tree

Binary Tree Target-Sum Paths

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ByteDanceNEW GRADPHONE SCREEN

Problem statement

Given the root of a binary tree and an integer targetSum, return every root-to-leaf path whose node values add up to targetSum.

A leaf is a node with no left child and no right child. Each returned path lists its values from the root to that leaf.

Return qualifying paths in left-to-right depth-first order: completely visit a node's left subtree before its right subtree.

Function

pathSum(root: TreeNode, targetSum: int) → int[][]

Examples

Example 1

root = [5,4,8,11,null,13,4,7,2,null,null,5,1]targetSum = 22return = [[5,4,11,2],[5,8,4,5]]

The two left-to-right root-to-leaf paths with sum 22 are 5 → 4 → 11 → 2 and 5 → 8 → 4 → 5.

Example 2

root = [1,2,3]targetSum = 5return = []

The two root-to-leaf sums are 3 and 4, so neither path qualifies.

Example 3

root = []targetSum = 0return = []

An empty tree has no root-to-leaf paths.

Constraints

The tree contains at most 5000 nodes.
Each node value is between -1000 and 1000, inclusive.
-10^9 <= targetSum <= 10^9.