【Leetcode】Binary Tree Paths

题目链接：https://leetcode.com/problems/binary-tree-paths/

题目：

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"]

思路：

难点在于要　路径要作为参数传入

算法：

	List<String> strList = new ArrayList<String>();

	public List<String> binaryTreePaths(TreeNode root) {
		if (root != null) {
			findPath(root, String.valueOf(root.val));
		}
		return strList;
	}

	public void findPath(TreeNode p, String path) {
		if (p.left == null && p.right == null)
			strList.add(path);
		if (p.left != null)
			findPath(p.left, path + "->" + p.left.val);
		if (p.right != null)
			findPath(p.right, path + "->" + p.right.val);
	}