Given a binary tree, return all root-to-leaf paths.
For example, given the following binary tree:
1 / 2 3 5
All root-to-leaf paths are:
["1->2->5", "1->3"]
[LeetCode] Binary Tree Paths 二叉树路径
原文：http://www.cnblogs.com/grandyang/p/4738031.html
