129. 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.

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Solution:

Tips:

tree, recursion

Java Code:

/** * Definition for a binary tree node. * public class TreeNode { *     int val; *     TreeNode left; *     TreeNode right; *     TreeNode(int x) { val = x; } * } */public class Solution {    public int sumNumbers(TreeNode root) {        if (null == root) {            return 0;        }                int[] sum = {0};        sumNumbers(root, "", sum);                return sum[0];    }        private void sumNumbers(TreeNode root, String s, int[] sum) {        if (root == null) {            return;        }        if (root.left == null && root.right == null) {            sum[0] += Integer.valueOf(s + root.val);        }                if (root.left != null) {            sumNumbers(root.left, s + root.val, sum);        }        if (root.right != null) {            sumNumbers(root.right, s + root.val, sum);        }    }}