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原创哦豁，我玩球了

转行了转行了，跨行如隔山，去做射频去了。

2023-09-20 14:46:33 52

原创 95. Unique Binary Search Trees II. Sol

官方解答写的很好搬运一下Given an integern, returnall the structurally uniqueBST's (binary search trees), which has exactlynnodes of unique values from1ton. Return the answer inany order.Example 1:Input: n = 3Output: [[1,null,2,null,3],[1,null,3,2],...

2022-02-23 21:23:20 99

原创 779. K-th Symbol in Grammar. Sol

这个题目是没有官方Sol的。用循环是不可以解出的(Memory or Time exceeded)，罕见的必须要用递归的题目，而且递归的写法也很优雅We build a table ofnrows (1-indexed). We start by writing0in the1strow. Now in every subsequent row, we look at the previous row and replace each occurrence of0with01, and...

2022-02-22 18:57:36 127

原创满血复活～喵呜～喵～呜～

满血复活

2022-02-20 18:35:43 85

原创 50. Pow(x, n). O(logN) Sol

搬运一下官方解答的二分法，时间复杂度为O(log)Implementpow(x, n), which calculatesxraised to the powern(i.e.,xn).Example 1:Input: x = 2.00000, n = 10Output: 1024.00000Example 2:Input: x = 2.10000, n = 3Output: 9.26100Example 3:Input: x = 2.00000, n...

2022-02-14 03:35:21 269

原创 70. Climbing Stairs. Iter--Sol

也是斐波那契数列的变体。区别是初始项不同。如果直接用递归做会比较耗时You are climbing a staircase. It takesnsteps to reach the top.Each time you can either climb1or2steps. In how many distinct ways can you climb to the top?Example 1:Input: n = 2Output: 2Explanation: There...

2022-02-14 03:20:08 212

原创 509. Fibonacci Number. Sol

还是Easy的题目，所以多做一点提升自信心（bushi）用递归很简单，不过这里不是用递归做的，是用普通的迭代，只需要一个for循环就够了TheFibonacci numbers, commonly denotedF(n)form a sequence, called theFibonacci sequence, such that each number is the sum of the two preceding ones, starting from0and1. That is,...

2022-02-14 03:10:38 139

原创 119. Pascal‘s Triangle II. Sol

Easy难度的题目，其实是二项式展开，不需要递归就可以了Given an integerrowIndex, return therowIndexth(0-indexed) row of thePascal's triangle.InPascal's triangle, each number is the sum of the two numbers directly above it as shown:Example 1:Input: rowIndex = 3O...

2022-02-14 01:50:21 180

原创 700. Search in a Binary Search Tree. Sol

是一道Easy题目，但是想要写的简洁一点也不容易You are given therootof a binary search tree (BST) and an integerval.Find the node in the BST that the node's value equalsvaland return the subtree rooted with that node. If such a node does not exist, returnnull.Examp...

2022-02-13 21:11:59 136

原创 344. Reverse String. Sol

搬运的官方sol，感觉不用区分奇偶还是不错滴Write a function that reverses a string. The input string is given as an array of characterss.You must do this by modifying the input arrayin-placewithO(1)extra memory.Example 1:Input: s = ["h","e","l","l","o"]Output:...

2022-02-13 19:22:30 182

原创 236. Lowest Common Ancestor of a Binary Tree. Sol

只需要遍历两次的解法Given a binary tree, find the lowest common ancestor (LCA) of two given nodes in the tree.According to thedefinition of LCA on Wikipedia: “The lowest common ancestor is defined between two nodespandqas the lowest node inTthat has both...

2022-02-12 18:16:21 240

原创 297. Serialize and Deserialize Binary Tree. Sol

懒得写了。。直接搬运一下官方答案Serialization is the process of converting a data structure or object into a sequence of bits so that it can be stored in a file or memory buffer, or transmitted across a network connection link to be reconstructed later in the same or an

2022-02-12 16:27:08 73

原创 117. Populating Next Right Pointers in Each Node II. Sol

自己写的普通层序遍历from collections import dequeclass Solution: def connect(self, root): if not root or (root.left==None and root.right==None): return root queue = deque([root,]) while queue: # number of elem

2022-02-12 00:58:57 155

原创 117. Populating Next Right Pointers in Each Node II. Sol

官方解答写的非常好，搬运一下class Solution: def processChild(self, childNode, prev, leftmost): if childNode: # If the "prev" pointer is alread set i.e. if we # already found atleast one node on the next level,

2022-02-12 00:54:18 539

原创前序和中序遍历重建二叉树--105. Construct Binary Tree from Preorder and Inorder Traversal. Sol

Given two integer arrayspreorderandinorderwherepreorderis the preorder traversal of a binary tree andinorderis the inorder traversal of the same tree, construct and returnthe binary tree.Example 1:Input: preorder = [3,9,20,15,7], inorder ...

2022-02-11 18:40:25 163

原创后序和中序遍历重建二叉树--106. Construct Binary Tree from Inorder and Postorder Traversal. Sol

非常有意思的一道题Given two integer arraysinorderandpostorderwhereinorderis the inorder traversal of a binary tree andpostorderis the postorder traversal of the same tree, construct and returnthe binary tree.Example 1:Input: inorder = [9,3,15,20...

2022-02-11 18:18:55 302

原创妖梦你还有很多幽灵要杀

2022-02-11 16:27:20 170

原创 250. Count Univalue Subtrees. Sol

不讲武德地使用了set()函数Given therootof a binary tree, return the number ofuni-valuesubtrees.Auni-value subtreemeans all nodes of the subtree have the same value.Example 1:Input: root = [5,1,5,5,5,null,5]Output: 4Example 2:Input: root = []...

2022-02-11 16:22:26 86

原创 112. Path Sum. Sol

Recursion 简洁的递归算法Given therootof a binary tree and an integertargetSum, returntrueif the tree has aroot-to-leafpath such that adding up all the values along the path equalstargetSum.Aleafis a node with no children.Example 1:Input: ...

2022-02-10 20:48:32 250

原创 101. Symmetric Tree. Sol

提供一种很有意思的递归解法Given therootof a binary tree,check whether it is a mirror of itself(i.e., symmetric around its center).Example 1:Input: root = [1,2,2,3,4,4,3]Output: trueExample 2:Input: root = [1,2,2,null,3,null,3]Output: false...

2022-02-10 19:44:20 182

原创 104. Maximum Depth of Binary Tree. Sol

Given therootof a binary tree, returnits maximum depth.A binary tree'smaximum depthis the number of nodes along the longest path from the root node down to the farthest leaf node.from collections import dequeclass Solution: def maxDepth(self...

2022-02-10 16:34:09 155

原创二叉树Morris遍历——Binary Tree Morris Traversal without Modifying Tree

基于官方解答的改进，Morris Traversal 且不用更改原来树的结构Morris原文Traversing binary trees simply and cheaply - ScienceDirectPreOrder 前序遍历 class Solution(object): def preorderTraversal(self, root): node, output = root, [] while node: i

2022-02-10 02:40:32 368

原创 61. Rotate List. Sol

Given theheadof a linkedlist, rotate the list to the right bykplaces.Example 1:Input: head = [1,2,3,4,5], k = 2Output: [4,5,1,2,3]Example 2:Input: head = [0,1,2], k = 4Output: [2,0,1]Constraints:The number of nodes in the l...

2022-02-06 02:18:00 271

原创 138. Copy List with Random Pointer. Sol

LeetCode官方教程参考答案，穷学生只充了一个月的会员，记录下来备忘A linked list of lengthnis given such that each node contains an additional random pointer, which could point to any node in the list, ornull.Construct adeep copyof the list. The deep copy should consist of exac...

2022-02-06 00:11:58 55

原创 708. Insert into a Sorted Circular Linked List. Sol

Given a Circular Linked List node, which is sorted in ascending order, write a function to insert a valueinsertValinto the list such that it remains a sorted circular list. The given node can be a reference to any single node in the list and may not nece..

2022-02-05 23:49:58 296

原创 430. Flatten a Multilevel Doubly Linked List. Sol

You are given a doubly linked list, which contains nodes that have a next pointer, a previous pointer, and an additionalchild pointer. This child pointer may or may not point to a separate doubly linked list, also containing these special nodes. These chi.

2022-02-05 22:19:35 77

原创 2. Add Two Numbers. Sol

重点是添加新的结点。You are given twonon-emptylinked lists representing two non-negative integers. The digits are stored inreverse order, and each of their nodes contains a single digit. Add the two numbers and return the sumas a linked list.You may assume t...

2022-02-05 19:35:08 706

原创 21. Merge Two Sorted Lists. Sol

LeetCode官方教程参考答案，穷学生只充了一个月的会员，记录下来备忘You are given the heads of two sorted linked listslist1andlist2.Merge the two lists in a onesortedlist. The list should be made by splicing together the nodes of the first two lists.Returnthe head of the merg...

2022-02-05 17:10:01 41

原创 203. Remove Linked List Elements. Sol

Given theheadof a linked list and an integerval, remove all the nodes of the linked list that hasNode.val == val, and returnthe new head.Example 1:Input: head = [1,2,6,3,4,5,6], val = 6Output: [1,2,3,4,5]Example 2:Input: head = [], val...

2022-02-04 06:12:58 583

原创 206. Reverse Linked List. Sol

LeetCode官方教程参考答案，穷学生只充了一个月的会员，记录下来备忘本专栏无以上特殊说明的其他Sol是自己写的Given theheadof a singly linked list, reverse the list, and returnthe reversed list.Example 1:Input: head = [1,2,3,4,5]Output: [5,4,3,2,1]Example 2:Input: head = [1,2]Outp...

2022-02-04 05:05:16 392

原创 19. Remove Nth Node From End of List. Sol

Given theheadof a linked list, remove thenthnode from the end of the list and return its head.Example 1:Input: head = [1,2,3,4,5], n = 2Output: [1,2,3,5]Example 2:Input: head = [1], n = 1Output: []Example 3:Input: head = [1,2], n...

2022-02-04 04:30:26 784

原创 160. Intersection of Two Linked Lists.Sol

Given the heads of two singly linked-listsheadAandheadB, returnthe node at which the two lists intersect. If the two linked lists have no intersection at all, returnnull.For example, the following two linked lists begin to intersect at nodec1:T...

2022-02-04 00:29:20 60

原创 142. Linked List Cycle II .Sol

总之官方答案是错的。。。下面是自己写的O(1)解法，缺点是比较慢。。。Given theheadof a linked list, returnthe node where the cycle begins. If there is no cycle, returnnull. （其实应该是None，太久没写Python了比较生，语法都不会了）There is a cycle in a linked list if there is some node in the list that c...

2022-02-03 21:02:16 775

原创希望接下来的一年能继续努力呀～

首先每日一问自己啥时候写完leetcode

2022-02-03 19:46:27 429

原创 LeetCode 141. Linked List Cycle Sol.

LeetCode官方教程参考答案，穷学生只充了一个月的会员，记录下来备忘Givenhead, the head of a linked list, determine if the linked list has a cycle in it.There is a cycle in a linked list if there is some node in the list that can be reached again by continuously following thenextp...

2022-01-29 18:06:41 217

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