LeetCode 257 Binary Tree Paths

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"]

采用递归：

public List<String> binaryTreePaths(TreeNode root) {
		List<String> paths = new ArrayList<String>();
		if (root == null) return paths;
		if (root.left == null && root.right == null) {
			paths.add(root.val + "");
			return paths;
		}
		List<String> left = binaryTreePaths(root.left);
		List<String> right = binaryTreePaths(root.right);
		for (String tmp : left) {
			paths.add(root.val + "->" + tmp);
		}
		for (String tmp : right) {
			paths.add(root.val + "->" + tmp);
		}
		return paths;
	}