moonlightshadow123
6/22/2017 - 2:39 PM

129. Sum Root to Leaf Numbers

  1. Sum Root to Leaf Numbers
# 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 sumNumbers(self, root):
        """
        :type root: TreeNode
        :rtype: int
        """
        self.total = 0
        self.DFS(root, 0)
        return self.total
    def DFS(self, node, curSum):
        if node == None:
            return 
        curSum = curSum*10 + node.val
        if node.left == None and node.right == None:
            self.total += curSum
        if node.left:
            self.DFS(node.left, curSum)
        if node.right:
            self.DFS(node.right, curSum)

https://leetcode.com/problems/sum-root-to-leaf-numbers/#/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.

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.