【Description】
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.
Note: A leaf is a node with no children.
Example:
Input: [1,2,3]
1
/
2 3
Output: 25
Explanation:
The root-to-leaf path 1->2 represents the number 12.
The root-to-leaf path 1->3 represents the number 13.
Therefore, sum = 12 + 13 = 25.
Example 2:
Input: [4,9,0,5,1]
4
/
9 0
/
5 1
Output: 1026
Explanation:
The root-to-leaf path 4->9->5 represents the number 495.
The root-to-leaf path 4->9->1 represents the number 491.
The root-to-leaf path 4->0 represents the number 40.
Therefore, sum = 495 + 491 + 40 = 1026.
【Idea】
跟求path的题差不多， 只不过这里是num*10+node.val 在每层递归里作参数传递罢辽。
不再写了，木得意思
similar：257。
【Solution】
# Definition for a binary tree node.
# class TreeNode:
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
class Solution:
def __init__(self):
self.result = 0
def sumNumbers(self, root: TreeNode) -> int:
def recursion(root, num):
if not root:
return
num = num*10+root.val
if not root.left and not root.right: # 叶子节点
self.result += num
return
recursion(root.left, num)
recursion(root.right, num)
recursion(root, 0)
return self.result
