Grokking Tree Coding Patterns for Interviews
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Sum of Left Leaves (easy)
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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]
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  • 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]
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  • Expected Output: 1
  • Justification: The only left leaf node is 1 (left child of 2). So, the answer is 1.

Example 3:

  • Input: root = [1, null, 5, null, 4]
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  • Expected Output: 0
  • Justification: The tree doesn't have any left leaf node.

Constraints:

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

Try it yourself

Try solving this question here:

Python3
Python3
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