Sum Root to Leaf Numbers 07/26

Same with binary tree path

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.

A leaf is a node with no children.Have you met this question in a real interview? Yes

Example

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.

/**
 * Definition of TreeNode:
 * public class TreeNode {
 *     public int val;
 *     public TreeNode left, right;
 *     public TreeNode(int val) {
 *         this.val = val;
 *         this.left = this.right = null;
 *     }
 * }
 */

public class Solution {
    /**
     * @param root: the root of the tree
     * @return: the total sum of all root-to-leaf numbers
     */
     
    public int res = 0;
    public int sumNumbers(TreeNode root) {
        // write your code here
        
        
        
        
        
        return helper(root,root.val);
    }
    
    public int helper(TreeNode root,int sum){
        
        if(root == null){
            return 0;
        }
        
        if(root.left == null && root.right == null){
            return sum;
        }
        
        int left = 0, right = 0;
        if(root.left != null){
             left = helper(root.left,sum*10+root.left.val);
        }
        if(root.right != null){
            right = helper(root.right,sum*10+root.right.val);
        }
        
        return left+right;
        
    }
}