Description

Given a binary tree, return all root-to-leaf paths.

Solution

注意使用.pop 和copy.deepcopy管理路径

"""
Definition of TreeNode:
class TreeNode:
    def __init__(self, val):
        self.val = val
        self.left, self.right = None, None
"""
import copy
class Solution:
    """
    @param root: the root of the binary tree
    @return: all root-to-leaf paths
    """
    def find_path(self,root,path):
        if root.left is None and root.right is None:
            path.append(root.val)
            self.path.append( "->".join(map(str,path)) )
            path.pop()
            return root.val
        path.append(root.val)
        if root.left is not None:
            self.find_path(root.left,path)
        if root.right is not None:
            self.find_path(root.right,path)
        path.pop()
  
    def binaryTreePaths(self, root):
        # write your code here
        if root is None:
            return []
        self.path =[]
        self.find_path(root,[])
        return self.path
     

更简洁版本，不需要额外储存空间，将path直接转换为str存储

"""
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
        if root is None:
            return []
        if root.left is None and root.right is None:
            return [str(root.val)]
        left= []
        if root.left is not None:
            left =self.binaryTreePaths(root.left)
        right =[]
        if root.right is not None:
            right = self.binaryTreePaths(root.right)
        path =[]
        
        for p in right+left:
            path.append(str(root.val) + '->'+ p)
        return path