Grokking Tree Coding Patterns for Interviews
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Solution: Sum of Left Leaves

Problem Statement

Given the root of a binary tree, return the sum of all left leaves.

A leaf is a node that does not have any child nodes, and a left leaf is a leaf that is the left child of its parent.

Examples

Example 1:

  • Input: root = [3,5,10,null,null,8,7]
  • Expected Output: 13
  • Justification: The leaf nodes are 5, 8, and 7, but only 5 and 8 are left leaf nodes. So, sum of left leaf nodes are 5 + 8 = 13.

Example 2:

  • Input: root = [5, 3, 8, 2, 4, null, 6, 1]
  • Expected Output: 1

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