Question：
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
答案是二叉树的穷尽遍历：
C#版：
/** * Definition for binary tree * public class TreeNode { * public int val; * public TreeNode left; * public TreeNode right; * public TreeNode(int x) { val = x; } * } */ public class Solution { private int result=0; public int SumNumbers(TreeNode root) { if (root==null) { return 0; } Solve(root,0); return result; } public static void Solve(TreeNode root,int sum) { if(root.left==null&&root.right==null) result+=(sum*10+root.val); if(root.left!=null) Solve(root.left,sum*10+root.val); if(root.right!=null) Solve(root.right,sum*10+root.val); } }
这个结果是可以运行的。
其中有一个小问题，就是当result被声明为static变量之后，程序就报错。
目前不知道原因。
等待解答。
【leetcode】Sum Root to Leaf Numbers
原文：http://www.cnblogs.com/AeroFantasia/p/4391313.html