题目描述: 给出二叉树的根节点 root,树上每个节点都有一个不同的值. 如果节点值在 to_delete 中出现,我们就把该节点从树上删去,最后得到一个森林(一些不相交的树构成的集合). 返回森林中的每棵树.你可以按任意顺序组织答案. 示例: 输入:root = [1,2,3,4,5,6,7], to_delete = [3,5] 输出:[[1,2,null,4],[6],[7]] 提示: 树中的节点数最大为 1000.每个节点都有一个介于 1 到 1000 之间的值,且各不相同.to_del…

原题链接在这里:https://leetcode.com/problems/delete-nodes-and-return-forest/ 题目: Given the root of a binary tree, each node in the tree has a distinct value. After deleting all nodes with a value in to_delete, we are left with a forest (a disjoint union of…

756. 金字塔转换矩阵 """ 学到的新知识: from collections import defaultditc可以帮我们初始化字典,不至于取到某个不存在的值的时候报错.例如列表类型就会默认初始值为[],str对应的是空字符串,set对应set( ),int对应0 思路: 通过本层构建上一层(DFS,类似于全排列),看是否能构建成功(递归) """ from collections import defaultdict class Sol…

本文讲解有关树的习题中子树问题和新概念定义问题,也是有关树习题的最后一篇总结.前两篇请参考: LeetCode刷题总结-树篇(上) LeetCode刷题总结-树篇(中) 本文共收录9道题,7道中等题,2道困难题.本篇总结的知识点请参考下图: 1 新概念定义问题 本部分收录习题如下: 117.填充每个节点的下一个右侧节点指针II, 难度: 中等 297.二叉树的序列化与反序列化,难度:困难 114.二叉树展开为链表,难度: 中等 998.最大二叉树II, 难度:中等 834.树中距离之和,难度:困…

题目: Design a data structure that supports all following operations in average O(1) time.1.insert(val): Inserts an item val to the set if not already present.2.remove(val): Removes an item val from the set if present.3.getRandom: Returns a random elem…

作者: 负雪明烛 id: fuxuemingzhu 个人博客:http://fuxuemingzhu.cn/ 目录 题目描述 题目大意 解题方法 递归 日期 题目地址:https://leetcode.com/problems/delete-nodes-and-return-forest/ 题目描述 Given the root of a binary tree, each node in the tree has a distinct value. After deleting all nod…

Given a non-empty string s, you may delete at most one character. Judge whether you can make it a palindrome. Example 1: Input: "aba" Output: True Example 2: Input: "abca" Output: True Explanation: You could delete the character 'c'. 思…

题目如下: Given the root of a binary tree, each node in the tree has a distinct value. After deleting all nodes with a value in to_delete, we are left with a forest (a disjoint union of trees). Return the roots of the trees in the remaining forest.  You…

源代码地址:https://github.com/hopebo/hopelee 语言:C++ 301. Remove Invalid Parentheses Remove the minimum number of invalid parentheses in order to make the input string valid. Return all possible results. Note: The input string may contain letters other tha…

The Hamming distance between two integers is the number of positions at which the corresponding bits are different. Now your job is to find the total Hamming distance between all pairs of the given numbers. Example: Input: 4, 14, 2 Output: 6 Explanat…