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[129] Sum Root to Leaf Numbers

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

algorithms
Medium (40.23%)
Source Code: 129.sum-root-to-leaf-numbers.py
Total Accepted: 180K
Total Submissions: 427.8K
Testcase Example: '[1,2,3]'

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.

python

# 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
        """
        path = self.enumAllPath(root)

        return sum([int(item) for item in path])

    def enumAllPath(self, root):
        path = []
        self.helper(root, path)
        return path

    def helper(self, root, path, current=''):
        if not root: return
        current += str(root.val)
        if not root.left and not root.right:
            path.append(current)
        if root.left:
            self.helper(root.left, path, current)
        if root.right:
            self.helper(root.right, path, current)
        return