#404

Sum of Left Leaves

easy · verified · 62.4% accepted · 5,782 likes · top 64%

tree · depth-first search · breadth-first search · binary tree

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Description

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

A leaf is a node with no children. A left leaf is a leaf that is the left child of another node.

Example 1:

Input: root = [3,9,20,null,null,15,7]
Output: 24
Explanation: There are two left leaves in the binary tree, with values 9 and 15 respectively.

Example 2:

Input: root = [1]
Output: 0

Solution