Python Recursion Didn't Give Correct Result for "Sum of Left Leaves"
I Wrote a Code for the Leetcode Problem "108. Sum of Left Leaves" Using Recursion. It Didn't Give Me the Expected Result. # Definition for a Binary Tree Node...
I wrote a code for the leetcode problem "108. Sum of Left Leaves" using recursion. It didn't give me the expected result.
# Definition for a binary tree node.
# class TreeNode(object):
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
class Solution(object):
def sumOfLeftLeaves(self, root):
"""
:type root: TreeNode
:rtype: int
"""
if root is None:
return 0
ans = 0
if root.left and not root.left.left and not root.left.right:
ans += root.left.val
self.sumOfLeftLeaves(root.left)
self.sumOfLeftLeaves(root.right)
return ans
When the input is [3,9,20,null,null,15,7]
I expected a 24 to be returned, but the code only gave me 9
1 Answer
You aren't adding the results of the leaves below the root. You need this:
class Solution(object):
def sumOfLeftLeaves(self, root):
"""
:type root: TreeNode
:rtype: int
"""
if root is None:
return 0
ans = 0
if root.left and not root.left.left and not root.left.right:
ans += root.left.val
ans += self.sumOfLeftLeaves(root.left) + self.sumOfLeftLeaves(root.right)
return ans
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