"""   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.
   
   IDEA:
   1) update a global rootToLeaf number if and only if the node is a leaf
   
"""

class Solution129:
    pass

"""   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.
   
   IDEA:
   1) update a global rootToLeaf number if and only if the node is a leaf
   
"""

class Solution129:
    pass

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.        IDEA:    1) update a global rootToLeaf number if and only if the node is a leaf