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Sum Root to Leaf Numbers

描述

Given a binary tree containing digits from 0-9 only, each root-to-leaf path could represent a number.

An example is the root-to-leaf path 1->2->3 which represents the number 123.

Find the total sum of all root-to-leaf numbers.

For example,

    1
/ \
2 3

The root-to-leaf path 1->2 represents the number 12. The root-to-leaf path 1->3 represents the number 13.

Return the sum = 12 + 13 = 25.

分析

代码

# Sum root to leaf numbers
# 时间复杂度O(n),空间复杂度O(logn)
class Solution:
def sumNumbers(self, root):
return self.dfs(root, 0)

def dfs(self, root, sum):
if not root:
return 0
if not root.left and not root.right:
return sum * 10 + root.val

return self.dfs(root.left, sum * 10 + root.val) + \
self.dfs(root.right, sum * 10 + root.val)