257.binary-tree-paths.py

#
# @lc app=leetcode id=257 lang=python3
#
# [257] Binary Tree Paths
#
'''
Given the root of a binary tree, return all root-to-leaf paths in any order.
A leaf is a node with no children.

'''

# @lc code=start
# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def binaryTreePaths(self, root: Optional[TreeNode]) -> List[str]:
        if not root:
            return []
        res, stack = [], [(root, "")]
        while stack:
            node, ls = stack.pop()
            if not node.left and not node.right:
                res.append(ls+str(node.val))
            if node.right:
                stack.append((node.right, ls+str(node.val)+"->"))
            if node.left:
                stack.append((node.left, ls+str(node.val)+"->"))
        return res
        
# @lc code=end