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404. Sum of Left Leaves (Easy)

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

 

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

 

Constraints:

• The number of nodes in the tree is in the range [1, 1000].
• -1000 <= Node.val <= 1000

Related Topics

[Tree] [Depth-First Search] [Breadth-First Search] [Binary Tree]