CODE 4: Sum Root to Leaf Numbers

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 number123.

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.

 

My Code:

private int sum;public int sumNumbers(TreeNode root) {// Start typing your Java solution below// DO NOT write main() functionthis.sum = 0;dfs(root, 0);return this.sum;}private void dfs(TreeNode root, int val) {if (null == root) {return;}if (null == root.left && null == root.right) {this.sum += root.val + val * 10;}if (null != root.left) {dfs(root.left, val * 10 + root.val);}if (null != root.right) {dfs(root.right, val * 10 + root.val);}}