Medium

Quiz

#437 Path Sum III

APPROACH

Given the root of a binary tree and an integer targetSum, count every path that travels strictly downward (parent toward descendant) whose node values sum to targetSum. Paths may begin and end at any node.

Example 1:

Input: root = [10,5,-3,3,2,null,11,3,-2,null,1], targetSum = 8

Output: 3

Explanation: The paths that sum to 8 are shown.

Example 2:

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

Output: 3

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What is the optimal approach for this problem?