58. Sum Root to Leaf Numbers

/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public int sumNumbers(TreeNode root) {
        return sum(root, 0);
    }
   
    public int sum(TreeNode root, int temp) {
        if (root==null) return 0;
        temp = 10*temp + root.val;
        if (root.left==null && root.right==null) return temp;
        return (sum(root.left, temp) + sum(root.right, temp));
    }
}