129.md

129. 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.

Code

class Solution {
    public int sumNumbers(TreeNode root) {
        return sum(root, 0);
    }
    
    int sum(TreeNode root, int total){
        if(root == null){
            return 0;
        }else if(root.left == null && root.right == null){
            return total * 10 + root.val;
        }else{
            return sum(root.left, total * 10 + root.val) + sum(root.right, total * 10 + root.val);
        }
        
    } 
}