437-Path Sum 3

Leetcode 75-day challenge

So, the problem I chose for today is: Path Sum III

Before I start explaining the solution to this problem, I assume that the reader of this blog has a basic understanding of how Binary Search Trees (BST) work. If not, you can watch my YouTube video on the topic here:

Let’s start:

Given the root of a binary tree and an integer targetSum, return the number of paths where the sum of the values along the path equals targetSum.

The path does not need to start or end at the root or a leaf, but it must go downwards (i.e., travelling only from parent nodes to child nodes).

Example 1:

Taken from Leetcode

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

Constraints:

• The number of nodes in the tree is in the…