递归与二叉树_leetcode257

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


# 这是从底向上构建路径
# 从上到下构建路径则需要将path 作为参数传递到下一层 待完成  20190305
class Solution(object):
    def binaryTreePaths(self, root):
        """
        :type root: TreeNode
        :rtype: List[str]
        """

        res = []
        if not root:
            return  res
        if not root.left and not root.right:
            res.append(str(root.val))

        leftPaths = self.binaryTreePaths(root.left)

        for i in range(len(leftPaths)):
            res.append(str(root.val) + "->" +leftPaths[i])

        rightPaths = self.binaryTreePaths(root.right)
        for i in range(len(rightPaths)):
            res.append(str(root.val) + "->" + rightPaths[i])

        return res