SumRootToLeafNum.py

'''
 Sum Root to Leaf Number
'''
class Node(object):
 def __init__(self,val=None,left=None,right=None):
 self.val = val
 self.left = left
 self.right = right

def SumNumbers(root):
 return SumRootToLeaf(root,0)

def SumRootToLeaf(root,total) :
 '''
 Args: a binary tree containing digits from 0-9 only, 
 each root to leaf path represent a number

 Return: total sum of all root to leaf numbers
 For example,
 1
 2 3
 represents as 123, 1->2 represents 12, 1->3 represents 13
 return the sum = 12 + 13 = 25
 '''
 if root is None :
 return 0
 total = total * 10 + root.val
 if root.left is None and root.right is None:
 return total
 else : 
 return SumRootToLeaf(root.left,total) + SumRootToLeaf(root.right,total)

root = Node(1,Node(2,Node(4)),Node(3))

print SumNumbers(root)