给定一个二叉树，返回所有从根节点到叶子节点的路径。

说明: 叶子节点是指没有子节点的节点。

示例:

输入:   1 /   \2     3 \  5输出: ["1->2->5", "1->3"]解释: 所有根节点到叶子节点的路径为: 1->2->5, 1->3

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

 

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