Leetcode 257. Binary Tree Paths

Description: Given the root of a binary tree, return all root-to-leaf paths in any order.

A leaf is a node with no children.

Link: 257. Binary Tree Paths

Examples:

Example 1:

Input: root = [1,2,3,null,5]
Output: ["1->2->5","1->3"]

Example 2:
Input: root = [1]
Output: ["1"]

思路: 返回所有从root到叶子节点的路径，又是返回所有解，回溯法。

class Solution(object):
    def binaryTreePaths(self, root):
        """
        :type root: TreeNode
        :rtype: List[str]
        """
        self.res = []
        self.dfs(root, '')
        return self.res
    
    def dfs(self, root, path):
        if not root.left and not root.right:
            path += '->'+str(root.val)
            self.res.append(path[2:])
            return
        if root.left:
            self.dfs(root.left, path+'->'+str(root.val))
        if root.right:
            self.dfs(root.right, path+'->'+str(root.val))

日期: 2021-04-19