【leetcode 简单】 第七十一题 二叉树的所有路径

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution:
    def binaryTreePaths(self, root):
        """
        :type root: TreeNode
        :rtype: List[str]
        """
        path=''
        result=[]
        self.echo(root,path,result)
        return result
    def echo(self,root,path,result):
        if not root:
            return 
        path+=str(root.val)
        if root.left:
            self.echo(root.left,path + '->',result)
        if root.right:
            self.echo(root.right,path + '->',result)
        if not root.left and not root.right:
            result.append(path)