[leetcode] SumRoottoLeafNumbers

package leetcode;

/**
* <pre>
* 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.
* </pre>
* */
public class SumRoottoLeafNumbers {
    public class TreeNode {
        int      val;
        TreeNode left;
        TreeNode right;

        TreeNode(int x) {
            val = x;
        }
    }

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