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
Constraints:
- The number of nodes in the tree is in the range
[1, 1000].
1000 <= Node.val <= 1000
problem link:
https://leetcode.com/problems/sum-of-left-leaves/
Given the
rootof 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
Constraints:
[1, 1000].1000<= Node.val <=1000problem link:
https://leetcode.com/problems/sum-of-left-leaves/