五. 二叉树 2 Binary Tree Paths

思路：

1. DFS
   注意每个path都应该是独立的，相互之间不存在包含和被包含的关系。

"""
Definition of TreeNode:
class TreeNode:
    def __init__(self, val):
        self.val = val
        self.left, self.right = None, None
"""


class Solution:
    """
    @param: root: the root of the binary tree
    @return: all root-to-leaf paths
    """
    def binaryTreePaths(self, root):
        # write your code here
        self.path = []
        if root == None:
            return self.path
        way = str(root.val)
        
        def dfs(root, way):
            if root.left == None and root.right == None:
                self.path.append(way)
                return
            
            if root.left:
                dfs(root.left, way + "->" + str(root.left.val))
            
            if root.right:
                dfs(root.right, way + "->" + str(root.right.val))
                    
        dfs(root, way)
        return self.path