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.
public int SumNumbers(TreeNode root) { return SumSub(root,0); } public int SumSub(TreeNode root, int num) { if(root == null) return num; int nextNum = num*10 + root.val; if(root.left == null && root.right == null) return num*10 + root.val; if(root.left == null) return SumSub(root.right,nextNum); if(root.right == null) return SumSub(root.left,nextNum); return SumSub(root.left,nextNum) + SumSub(root.right,nextNum); }
原文：http://www.cnblogs.com/renyualbert/p/5875688.html