leetCode笔记

LeetCode笔记：83. Remove Duplicates from Sorted List

问题：Givenasortedlinkedlist,deleteallduplicatessuchthateachelementappearonlyonce.Forexample,Given1->1->2,return1->2.Given1->1->2->3->3,return1->2->3.大意：给出一个排好序的链表，删除所有的重复的数字，让每个元素只出现一次。比如：给出1->1->2,返回1-
Cloudox_·2020-02-21 20:55

LeetCode笔记：415. Add Strings

问题：Giventwonon-negativenumbersnum1andnum2representedasstring,returnthesumofnum1andnum2.Note:1、Thelengthofbothnum1andnum2is=0||j>=0){intn1=i>=0?num1.charAt(i)-'0':0;intn2=j>=0?num2.charAt(j)-'0':0;ints
Cloudox_·2020-02-21 12:52

LeetCode笔记：503. Next Greater Element II

问题：Givenacirculararray(thenextelementofthelastelementisthefirstelementofthearray),printtheNextGreaterNumberforeveryelement.TheNextGreaterNumberofanumberxisthefirstgreaternumbertoitstraversing-ordernex
Cloudox_·2020-02-21 05:56

LeetCode笔记-0004-寻找两个有序数组的中位数

题目信息给定两个大小为m和n的有序数组nums1和nums2。请你找出这两个有序数组的中位数，并且要求算法的时间复杂度为O(log(m+n))。你可以假设nums1和nums2不会同时为空。示例1:nums1=[1,3]nums2=[2]则中位数是2.0示例2:nums1=[1,2]nums2=[3,4]则中位数是(2+3)/2=2.5来源：力扣（LeetCode）链接：https://leetc
dragonMen·2020-02-19 02:06

LeetCode笔记：338. Counting Bits

问题：Givenanonnegativeintegernumbernum.Foreverynumbersiintherange0≤i≤numcalculatethenumberof1'sintheirbinaryrepresentationandreturnthemasanarray.Example:Fornum=5youshouldreturn[0,1,1,2,1,2].Followup:Iti
Cloudox_·2020-02-17 20:34

LeetCode笔记：539. Minimum Time Difference

问题：Givenalistof24-hourclocktimepointsin"Hour:Minutes"format,findtheminimumminutesdifferencebetweenanytwotimepointsinthelist.Example1:Input:["23:59","00:00"]Output:1Note:Thenumberoftimepointsinthegiven
Cloudox_·2020-02-16 02:52

LeetCode笔记：454. 4Sum II

问题：GivenfourlistsA,B,C,Dofintegervalues,computehowmanytuples(i,j,k,l)therearesuchthatA[i]+B[j]+C[k]+D[l]iszero.Tomakeproblemabiteasier,allA,B,C,DhavesamelengthofNwhere0≤N≤500.Allintegersareintherangeo
Cloudox_·2020-02-15 15:50

LeetCode笔记：242. Valid Anagram

题目：Giventwostringssandt,writeafunctiontodetermineiftisananagramofs.Forexample,s="anagram",t="nagaram",returntrue.s="rat",t="car",returnfalse.Note:Youmayassumethestringcontainsonlylowercasealphabets.Fo
Cloudox_·2020-02-15 05:09

LeetCode笔记：94. Binary Tree Inorder Traversal

问题：Givenabinarytree,returntheinordertraversalofitsnodes'values.Forexample:Givenbinarytree[1,null,2,3],image.pngreturn[1,3,2].Note:Recursivesolutionistrivial,couldyoudoititeratively?大意：给出一个二叉树，返回中序遍历的节
Cloudox_·2020-02-13 06:58

LeetCode笔记：653. Two Sum IV - Input is a BST

问题（Easy）：GivenaBinarySearchTreeandatargetnumber,returntrueifthereexisttwoelementsintheBSTsuchthattheirsumisequaltothegiventarget.Example1:Input:Target=9Output:TrueExample2:Input:Target=28Output:False大
Cloudox_·2020-02-12 10:57

LeetCode笔记：566. Reshape the Matrix

问题（Easy）：InMATLAB,thereisaveryusefulfunctioncalled'reshape',whichcanreshapeamatrixintoanewonewithdifferentsizebutkeepitsoriginaldata.You'regivenamatrixrepresentedbyatwo-dimensionalarray,andtwopositive
Cloudox_·2020-02-12 10:08

LeetCode笔记：459. Repeated Substring Pattern

问题：Givenanon-emptystringcheckifitcanbeconstructedbytakingasubstringofitandappendingmultiplecopiesofthesubstringtogether.YoumayassumethegivenstringconsistsoflowercaseEnglishlettersonlyanditslengthwilln
Cloudox_·2020-02-07 00:26

LeetCode笔记：696. Count Binary Substrings

问题（Easy）：Giveastrings,countthenumberofnon-empty(contiguous)substringsthathavethesamenumberof0'sand1's,andallthe0'sandallthe1'sinthesesubstringsaregroupedconsecutively.Substringsthatoccurmultipletimesa
Cloudox_·2020-02-05 01:50

LeetCode笔记：524. Longest Word in Dictionary through Deleting

问题：Givenastringandastringdictionary,findthelongeststringinthedictionarythatcanbeformedbydeletingsomecharactersofthegivenstring.Iftherearemorethanonepossibleresults,returnthelongestwordwiththesmallestl
Cloudox_·2020-01-05 08:24

LeetCode笔记：515. Find Largest Value in Each Tree Row

问题：Youneedtofindthelargestvalueineachrowofabinarytree.Example:Input:image.pngOutput:[1,3,9]大意：你需要找到二叉树中每一行最大的值。例子：输入：image.png输出：[1,3,9]思路：要找每一行最大的数，我们总归是要遍历二叉树的，遍历二叉树分为BFS和DFS，这里我们要找每行最大的数，那么我们就用BFS，
Cloudox_·2020-01-02 03:32

LeetCode笔记：110. Balanced Binary Tree

问题：Givenabinarytree,determineifitisheight-balanced.Forthisproblem,aheight-balancedbinarytreeisdefinedasabinarytreeinwhichthedepthofthetwosubtreesofeverynodeneverdifferbymorethan1.大意：给出一个二叉树，判断它高度是不是平衡
Cloudox_·2020-01-01 21:11

LeetCode笔记：762. Prime Number of Set Bits in Binary Representation

问题（Easy）：GiventwointegersLandR,findthecountofnumbersintherange[L,R](inclusive)havingaprimenumberofsetbitsintheirbinaryrepresentation.(Recallthatthenumberofsetbitsanintegerhasisthenumberof1spresentwhen
Cloudox_·2020-01-01 14:35

LeetCode笔记：6. ZigZag Conversion

问题：Thestring"PAYPALISHIRING"iswritteninazigzagpatternonagivennumberofrowslikethis:(youmaywanttodisplaythispatterninafixedfontforbetterlegibility)PAHNAPLSIIGYIRAndthenreadlinebyline:"PAHNAPLSIIGYIR"Wri
Cloudox_·2020-01-01 07:42

LeetCode笔记：137. Single Number II

问题：Givenanarrayofintegers,everyelementappearsthreetimesexceptforone,whichappearsexactlyonce.Findthatsingleone.Note:Youralgorithmshouldhavealinearruntimecomplexity.Couldyouimplementitwithoutusingextram
Cloudox_·2020-01-01 04:19

LeetCode笔记：104.Maximum Depth of Binary Tree

问题：Givenabinarytree,finditsmaximumdepth.Themaximumdepthisthenumberofnodesalongthelongestpathfromtherootnodedowntothefarthestleafnode.大意：给出一个二叉树，找到其最大的深度。最大深度是指从根节点到最远的叶子节点的最长距离的节点数。思路：要探索二叉树的深度，用递归比较方
Cloudox_·2019-12-31 23:23

LeetCode笔记：394. Decode String

问题：Givenanencodedstring,returnit'sdecodedstring.Theencodingruleis:k[encoded_string],wheretheencoded_stringinsidethesquarebracketsisbeingrepeatedexactlyktimes.Notethatkisguaranteedtobeapositiveinteger.
Cloudox_·2019-12-31 22:12

LeetCode笔记：345. Reverse Vowels of a String

问题：Writeafunctionthattakesastringasinputandreverseonlythevowelsofastring.Example1:Givens="hello",return"holle".Example2:Givens="leetcode",return"leotcede".Note:Thevowelsdoesnotincludetheletter"y".大意：写
Cloudox_·2019-12-31 10:08

LeetCode笔记：8. String to Integer (atoi)

问题：Implementatoitoconvertastringtoaninteger.Hint:Carefullyconsiderallpossibleinputcases.Ifyouwantachallenge,pleasedonotseebelowandaskyourselfwhatarethepossibleinputcases.Notes:Itisintendedforthisprobl
Cloudox_·2019-12-31 01:35

LeetCode笔记：226. Invert Binary Tree

问题：Invertabinarytree.image.pngtoimage.pngTrivia:Google:90%ofourengineersusethesoftwareyouwrote(Homebrew),>butyoucan’tinvertabinarytreeonawhiteboardsofuckoff.大意：反转一个二叉树。从image.png到image.png琐事：Google表示如
Cloudox_·2019-12-29 20:20

LeetCode笔记-0002-两数相加

题目信息给出两个非空的链表用来表示两个非负的整数。其中，它们各自的位数是按照逆序的方式存储的，并且它们的每个节点只能存储一位数字。如果，我们将这两个数相加起来，则会返回一个新的链表来表示它们的和。您可以假设除了数字0之外，这两个数都不会以0开头。示例：输入：(2->4->3)+(5->6->4)输出：7->0->8原因：342+465=807来源：力扣（LeetCode）链接：https://le
dragonMen·2019-12-28 07:26

LeetCode笔记：513. Find Bottom Left Tree Value

问题：Givenabinarytree,findtheleftmostvalueinthelastrowofthetree.Example1:Input:image.pngOutput:1Example2:Input:image.pngOutput:7Note:Youmayassumethetree(i.e.,thegivenrootnode)isnotNULL.大意：给出一个二叉树，找到树最下一
Cloudox_·2019-12-27 08:08

LeetCode笔记：414. Third Maximum Number

问题：Givenanon-emptyarrayofintegers,returnthethirdmaximumnumberinthisarray.Ifitdoesnotexist,returnthemaximumnumber.ThetimecomplexitymustbeinO(n).Example1:Input:[3,2,1]Output:1Explanation:Thethirdmaximum
Cloudox_·2019-12-25 05:11

LeetCode笔记：257. Binary Tree Paths

问题：Givenabinarytree,returnallroot-to-leafpaths.Forexample,giventhefollowingbinarytree:image.pngAllroot-to-leafpathsare:["1->2->5","1->3"]大意：给出一个二叉树，返回所有从根节点到叶子节点的路径。比如给出下面这个二叉树：image.png所有从根节点到叶子节点的路径
Cloudox_·2019-12-24 15:39

LeetCode笔记：303. Range Sum Query - Immutable

问题：Givenanintegerarraynums,findthesumoftheelementsbetweenindicesiandj(i≤j),inclusive.Example:Givennums=[-2,0,3,-5,2,-1]sumRange(0,2)->1sumRange(2,5)->-1sumRange(0,5)->-3Note:Youmayassumethatthearraydo
Cloudox_·2019-12-24 05:34

LeetCode笔记：451. Sort Characters By Frequency

问题：Givenastring,sortitindecreasingorderbasedonthefrequencyofcharacters.Example1:Input:"tree"Output:"eert"Explanation:'e'appearstwicewhile'r'and't'bothappearonce.So'e'mustappearbeforeboth'r'and't'.Ther
Cloudox_·2019-12-23 17:11

LeetCode笔记：349. Intersection of Two Arrays

问题：Giventwoarrays,writeafunctiontocomputetheirintersection.Example:Givennums1=[1,2,2,1],nums2=[2,2],return[2].Note:Eachelementintheresultmustbeunique.Theresultcanbeinanyorder.大意：给出两个数组，写一个函数来计算他们的交叉点。
Cloudox_·2019-12-23 09:17

LeetCode笔记：111. Minimum Depth of Binary Tree

问题：Givenabinarytree,finditsminimumdepth.Theminimumdepthisthenumberofnodesalongtheshortestpathfromtherootnodedowntothenearestleafnode.大意：给出一个二叉树，找到他最小的深度。最小的深度是指从根节点到叶子节点距离最短的节点数。思路：这道题要找到最短的深度，个人认为更应该
Cloudox_·2019-12-23 06:40

LeetCode笔记：477. Total Hamming Distance

问题：TheHammingdistancebetweentwointegersisthenumberofpositionsatwhichthecorrespondingbitsaredifferent.NowyourjobistofindthetotalHammingdistancebetweenallpairsofthegivennumbers.Example:Input:4,14,2Outpu
Cloudox_·2019-12-22 05:43

LeetCode笔记：290. Word Pattern

问题：Givenapatternandastringstr,findifstrfollowsthesamepattern.Herefollowmeansafullmatch,suchthatthereisabijectionbetweenaletterinpatternandanon-emptywordinstr.Examples:pattern="abba",str="dogcatcatdog"
Cloudox_·2019-12-20 21:58

LeetCode笔记：20. Valid Parentheses

问题：Givenastringcontainingjustthecharacters'(',')','{','}','['and']',determineiftheinputstringisvalid.Thebracketsmustcloseinthecorrectorder,"()"and"()[]{}"areallvalidbut"(]"and"([)]"arenot.大意：给出一个只包含'(
Cloudox_·2019-12-20 10:34

LeetCode笔记：122. Best Time to Buy and Sell Stock II

问题：Sayyouhaveanarrayforwhichtheithelementisthepriceofagivenstockondayi.Designanalgorithmtofindthemaximumprofit.Youmaycompleteasmanytransactionsasyoulike(ie,buyoneandselloneshareofthestockmultipletimes
Cloudox_·2019-12-16 14:40

LeetCode笔记：219. Contains Duplicate II

问题：Givenanarrayofintegersandanintegerk,findoutwhethertherearetwodistinctindicesiandjinthearraysuchthatnums[i]=nums[j]andthedifferencebetweeniandjisatmostk.大意：给出一个整型数组和一个整型数k，判断数组中是否任何两个不一样的位置i和j，如果num
Cloudox_·2019-12-14 17:30

LeetCode笔记：112. Path Sum

问题：Givenabinarytreeandasum,determineifthetreehasaroot-to-leafpathsuchthataddingupallthevaluesalongthepathequalsthegivensum.Forexample:Giventhebelowbinarytreeandsum=22,image.pngreturntrue,asthereexista
Cloudox_·2019-12-12 09:10

LeetCode笔记：189. Rotate Array

问题：Rotateanarrayofnelementstotherightbyksteps.Forexample,withn=7andk=3,thearray[1,2,3,4,5,6,7]isrotatedto[5,6,7,1,2,3,4].大意：旋转一个有n个元素的数组，右移k步。比如，n=7，k=3，数组[1,2,3,4,5,6,7]就被旋转为[5,6,7,1,2,3,4]。思路：旋转本身没太
Cloudox_·2019-12-07 02:27

LeetCode笔记：238. Product of Array Except Self

问题：Givenanarrayofnintegerswheren>1,nums,returnanarrayoutputsuchthatoutput[i]isequaltotheproductofalltheelementsofnumsexceptnums[i].SolveitwithoutdivisionandinO(n).Forexample,given[1,2,3,4],return[24,1
Cloudox_·2019-12-06 15:05

LeetCode笔记：438. Find All Anagrams in a String

问题：Givenastringsandanon-emptystringp,findallthestartindicesofp'sanagramsins.StringsconsistsoflowercaseEnglishlettersonlyandthelengthofbothstringssandpwillnotbelargerthan20,100.Theorderofoutputdoesnotm
Cloudox_·2019-12-01 08:17

LeetCode笔记：486. Predict the Winner

问题：Givenanarrayofscoresthatarenon-negativeintegers.Player1picksoneofthenumbersfromeitherendofthearrayfollowedbytheplayer2andthenplayer1andsoon.Eachtimeaplayerpicksanumber,thatnumberwillnotbeavailablef
Cloudox_·2019-11-30 21:08

LeetCode笔记：234. Palindrome Linked List

问题：Givenasinglylinkedlist,determineifitisapalindrome.Followup:CouldyoudoitinO(n)timeandO(1)space?大意：给出一个单链表，判断它是否是回文。进阶：你能在O（n）的时间复杂度和O（1）的空间复杂度下来做吗？思路：回文的意思就是正着读反着读都是一样的。这道题我使用简单的思路，一个个遍历链表节点来倒序组成一个新
Cloudox_·2019-11-29 23:31

LeetCode笔记：205. Isomorphic Strings

问题：Giventwostringssandt,determineiftheyareisomorphic.Twostringsareisomorphicifthecharactersinscanbereplacedtogett.Alloccurrencesofacharactermustbereplacedwithanothercharacterwhilepreservingtheorderofc
Cloudox_·2019-11-29 18:14

LeetCode笔记：38. Count and Say

问题：Thecount-and-saysequenceisthesequenceofintegersbeginningasfollows:1,11,21,1211,111221,...1isreadoffas"one1"or11.11isreadoffas"two1s"or21.21isreadoffas"one2,thenone1"or1211.Givenanintegern,generatet
Cloudox_·2019-11-28 01:09

LeetCode笔记：102. Binary Tree Level Order Traversal

问题：Givenabinarytree,returnthelevelordertraversalofitsnodes'values.(ie,fromlefttoright,levelbylevel).Forexample:Givenbinarytree[3,9,20,null,null,15,7],image.pngreturnitslevelordertraversalas:[[3],[9,20
Cloudox_·2019-11-07 11:20

LeetCode笔记：344. Reverse String

问题：Writeafunctionthattakesastringasinputandreturnsthestringreversed.Example:Givens="hello",return"olleh".大意：写一个函数获取输入的字符串然后返回反转后后的字符串。比如：给出s="hello"，返回"olleh"思路：思路很直接就想到，先把字符串拆分成一个个字符组成的数组，新建一个空字符串，然后
Cloudox_·2019-11-07 07:33

LeetCode笔记：326. Power of Three

问题：Givenaninteger,writeafunctiontodetermineifitisapowerofthree.Followup:Couldyoudoitwithoutusinganyloop/recursion?大意：给出一个整数，写一个函数来判断它是否是3的次方数。进阶：你能不能不用循环和递归来做？思路：一开始看这个题目没明白是什么意思，后来查了一下才知道是判断是否3的次方数，所
Cloudox_·2019-11-07 07:00

LeetCode笔记：404. Sum of Left Leaves

问题：Findthesumofallleftleavesinagivenbinarytree.Example:image.pngTherearetwoleftleavesinthebinarytree,withvalues9and15respectively.Return24.大意：计算一个二叉树中所有左叶子节点的和例子:image.png在这个二叉树中有两个左叶子节点，分别为9和15。因此返回2
Cloudox_·2019-11-06 03:06

LeetCode笔记：24. Swap Nodes in Pairs

问题：Givenalinkedlist,swapeverytwoadjacentnodesandreturnitshead.Forexample,Given1->2->3->4,youshouldreturnthelistas2->1->4->3.Youralgorithmshoulduseonlyconstantspace.Youmaynotmodifythevaluesinthelist,on
Cloudox_·2019-11-06 03:18
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