leetCode笔记

LeetCode笔记：392. Is Subsequence

问题：Givenastringsandastringt,checkifsissubsequenceoft.YoumayassumethatthereisonlylowercaseEnglishlettersinbothsandt.tispotentiallyaverylong(length~=500,000)string,andsisashortstring(=1B,andyouwanttoche
Cloudox_·2017-11-23 09:06

LeetCode笔记：445. Add Two Numbers II

问题：Youaregiventwonon-emptylinkedlistsrepresentingtwonon-negativeintegers.Themostsignificantdigitcomesfirstandeachoftheirnodescontainasingledigit.Addthetwonumbersandreturnitasalinkedlist.Youmayassumeth
Cloudox_·2017-11-23 09:52

LeetCode笔记：442. Find All Duplicates in an Array

问题：Givenanarrayofintegers,1≤a[i]≤n(n=sizeofarray),someelementsappeartwiceandothersappearonce.Findalltheelementsthatappeartwiceinthisarray.CouldyoudoitwithoutextraspaceandinO(n)runtime?Example:Input:[4
Cloudox_·2017-11-23 09:48

LeetCode笔记：462. Minimum Moves to Equal Array Elements II

问题：Givenanon-emptyintegerarray,findtheminimumnumberofmovesrequiredtomakeallarrayelementsequal,whereamoveisincrementingaselectedelementby1ordecrementingaselectedelementby1.Youmayassumethearray'slengthi
Cloudox_·2017-11-23 09:05

LeetCode笔记：165. Compare Version Numbers

问题：Comparetwoversionnumbersversion1andversion2.Ifversion1>version2return1,ifversion1version2就返回，如果version1b)return1;elseif(a
Cloudox_·2017-11-23 09:22

LeetCode笔记：168. Excel Sheet Column Title

问题：Givenapositiveinteger,returnitscorrespondingcolumntitleasappearinanExcelsheet.Forexample:1->A2->B3->C...26->Z27->AA28->AB大意：给出一个正整数，返回它对应的Excel表格中的列标题。例子：1->A2->B3->C...26->Z27->AA28->AB思路：我们找一下规律，
Cloudox_·2017-11-23 09:08

LeetCode笔记：125. Valid Palindrome

问题：Givenastring,determineifitisapalindrome,consideringonlyalphanumericcharactersandignoringcases.Forexample,"Aman,aplan,acanal:Panama"isapalindrome."raceacar"isnotapalindrome.Note:Haveyouconsiderthatt
Cloudox_·2017-11-23 09:35

LeetCode笔记：204. Count Primes

问题：Countthenumberofprimenumberslessthananon-negativenumber,n.大意：计算小于非负数n的质数个数。思路：题目很简短，就是个找质数的问题。我们知道最简单的质数就是2，3，5。。。那怎么计算往后的质数呢？质数的定义是除了自己以外没有任何因子，也就是不被任何数整除，也就是说，不会被这个数前面的任何质数和非质数整除，其实非质数也可以被质数整除，比如
Cloudox_·2017-11-22 16:50

LeetCode笔记：28. Implement strStr()

问题：ImplementstrStr().Returnstheindexofthefirstoccurrenceofneedleinhaystack,or-1ifneedleisnotpartofhaystack.大意：实现strStr()。返回haystack中第一次出现needle的位置，如果needle不是haystack的一部分则返回-1。思路：最简单的做法就是遍历haystack，发现和
Cloudox_·2017-11-22 16:04

LeetCode笔记：14. Longest Common Prefix

问题Writeafunctiontofindthelongestcommonprefixstringamongstanarrayofstrings.大意：写一个函数来寻找一个数组的字符串中最长的相同前缀。思路：题目描述很简单只有一句话，导致我理解错了，以为是找到存在的任意两个字符串最长的相同前缀，还写了一份代码出来，自己测试的时候发现题目想要的结果不符合才发现，其实是找整个数组的字符串都有的相同的
Cloudox_·2017-11-22 16:10

LeetCode笔记：58. Length of Last Word

问题：Givenastringsconsistsofupper/lower-casealphabetsandemptyspacecharacters'',returnthelengthoflastwordinthestring.Ifthelastworddoesnotexist,return0.Note:Awordisdefinedasacharactersequenceconsistsofnon
Cloudox_·2017-11-22 14:00

LeetCode笔记：299. Bulls and Cows

问题：YouareplayingthefollowingBullsandCowsgamewithyourfriend:Youwritedownanumberandaskyourfriendtoguesswhatthenumberis.Eachtimeyourfriendmakesaguess,youprovideahintthatindicateshowmanydigitsinsaidguessm
Cloudox_·2017-11-22 11:48

LeetCode笔记：172. Factorial Trailing Zeroes

问题：Givenanintegern,returnthenumberoftrailingzeroesinn!.Note:Yoursolutionshouldbeinlogarithmictimecomplexity.大意：给出一个整数n，返回n!后面0的个数。注意：你的算法时间复杂度要是logn以内。思路：这道题的要求是计算n的阶乘后面0的个数，而且要求算法时间复杂度为logn，那么就绝对不是要人
Cloudox_·2017-11-22 08:05

LeetCode笔记：66. Plus One

问题：Givenanon-negativenumberrepresentedasanarrayofdigits,plusonetothenumber.Thedigitsarestoredsuchthatthemostsignificantdigitisattheheadofthelist.大意：给出一个非负数的代表数字的数组，给这个“数字”加一。这个数字的存储形式为最高位的数再数组的最前端。思路：
Cloudox_·2017-11-21 10:50

LeetCode笔记：107. Binary Tree Level Order Traversal II

问题：Givenabinarytree,returnthebottom-uplevelordertraversalofitsnodes'values.(ie,fromlefttoright,levelbylevelfromleaftoroot).Forexample:Givenbinarytree[3,9,20,null,null,15,7],image.pngreturnitsbottom-up
Cloudox_·2017-11-21 10:49

LeetCode笔记：342. Power of Four

问题：Givenaninteger(signed32bits),writeafunctiontocheckwhetheritisapowerof4.Example:Givennum=16,returntrue.Givennum=5,returnfalse.Followup:Couldyousolveitwithoutloops/recursion?大意：给出一个数字（有符号32位），写一个函数来检
Cloudox_·2017-11-21 10:32

LeetCode笔记：70. Climbing Stairs

问题：Youareclimbingastaircase.Ittakesnstepstoreachtothetop.Eachtimeyoucaneitherclimb1or2steps.Inhowmanydistinctwayscanyouclimbtothetop?大意：你在爬一个楼梯。需要n节楼梯到达顶部。每次你可以爬一节或者两节楼梯。你总共有多少种爬到顶部的方法？思路：总觉得这个题目小时候做过
Cloudox_·2017-11-21 10:50

LeetCode笔记：191. Number of 1 Bits

问题：Writeafunctionthattakesanunsignedintegerandreturnsthenumberof’1'bitsithas(alsoknownastheHammingweight).Forexample,the32-bitinteger’11'hasbinaryrepresentation00000000000000000000000000001011,sothefu
Cloudox_·2017-11-21 10:51

LeetCode笔记：231. Power of Two

问题：Givenaninteger,writeafunctiontodetermineifitisapoweroftwo.大意：给出一个整数，写一个函数判断它是否是2的次方数。思路：这道题和另一道判断是否是3的次方数的题目很像，但是这个更简单，因为有一个二进制的东西存在，我们要判断一个数是不是2的次方数，不用去一次次除以2，也不用用log去算，直接转换成二进制，如果是2的次方数，那一定是最高位为1
Cloudox_·2017-11-21 09:16

LeetCode笔记：387. First Unique Character in a String

问题：Givenastring,findthefirstnon-repeatingcharacterinitandreturnit'sindex.Ifitdoesn'texist,return-1.Examples:s="leetcode"return0.s="loveleetcode",return2.Note:Youmayassumethestringcontainonlylowercasel
Cloudox_·2017-11-21 09:50

LeetCode笔记：389. Find the Difference

问题：Giventwostringssandtwhichconsistofonlylowercaseletters.Stringtisgeneratedbyrandomshufflingstringsandthenaddonemoreletteratarandomposition.Findtheletterthatwasaddedint.大意：给出两个完全有小写字母组成的字符串s和t。字符串t是由
Cloudox_·2017-11-21 09:43

LeetCode笔记：136. Single Number

问题：Givenanarrayofintegers,everyelementappearstwiceexceptforone.Findthatsingleone.Note:Youralgorithmshouldhavealinearruntimecomplexity.Couldyouimplementitwithoutusingextramemory?大意：给出一个整数数组，其中每个元素都出现了两
Cloudox_·2017-11-21 09:52

LeetCode笔记：171. Excel Sheet Column Number

题目：RelatedtoquestionExcelSheetColumnTitleGivenacolumntitleasappearinanExcelsheet,returnitscorrespondingcolumnnumber.Forexample:A->1B->2C->3...Z->26AA->27AB->28大意：与题目ExcelSheetColumnTitle相关给一个像Excel中显示
Cloudox_·2017-11-19 10:09

LeetCode笔记 -- LongestSubStringLength

拖了1天，今天顶着疲惫写了这篇笔记.这是最终完成的代码（借鉴了一部分网上的讨论）。publicintlengthOfLongestSubstring(Strings){intmaxlength=0,length=s.length(),t_location=0;int[]location=newint[256];for(inti=0;i0?Math.max(t_location,location[s
Mr_Carter·2017-10-03 23:37

LeetCode笔记：309. Best Time to Buy and Sell Stock with Cooldown

问题：Sayyouhaveanarrayforwhichtheithelementisthepriceofagivenstockondayi.Designanalgorithmtofindthemaximumprofit.Youmaycompleteasmanytransactionsasyoulike(ie,buyoneandselloneshareofthestockmultipletimes
Cloudox_·2017-04-26 10:54

LeetCode笔记：89. Gray Code

问题：Thegraycodeisabinarynumeralsystemwheretwosuccessivevaluesdifferinonlyonebit.Givenanon-negativeintegernrepresentingthetotalnumberofbitsinthecode,printthesequenceofgraycode.Agraycodesequencemustbegin
Cloudox_·2017-04-25 09:45

LeetCode笔记：96. Unique Binary Search Trees

问题：Givenn,howmanystructurallyuniqueBST’s(binarysearchtrees)thatstorevalues1…n?Forexample,Givenn=3,thereareatotalof5uniqueBST’s.大意：给出n，包含1~n这些节点可以形成多少个不同的BST（二叉查找树）？比如，给出n=3，有5个不同的BST：思路：二叉查找树的性质是左子节点一
Cloudox_·2017-04-19 09:40

LeetCode笔记：386. Lexicographical Numbers

问题：Givenanintegern,return1-ninlexicographicalorder.Forexample,given13,return:[1,10,11,12,13,2,3,4,5,6,7,8,9].Pleaseoptimizeyouralgorithmtouselesstimeandspace.Theinputsizemaybeaslargeas5,000,000.思路：给出一
Cloudox_·2017-04-18 09:04

LeetCode笔记：424. Longest Repeating Character Replacement

问题：GivenastringthatconsistsofonlyuppercaseEnglishletters,youcanreplaceanyletterinthestringwithanotherletteratmostktimes.Findthelengthofalongestsubstringcontainingallrepeatinglettersyoucangetafterperfo
Cloudox_·2017-04-08 20:13

LeetCode笔记：424. Longest Repeating Character Replacement

问题：GivenastringthatconsistsofonlyuppercaseEnglishletters,youcanreplaceanyletterinthestringwithanotherletteratmostktimes.Findthelengthofalongestsubstringcontainingallrepeatinglettersyoucangetafterperfo
Cloudox_·2017-04-08 20:13

LeetCode笔记：46. Permutations

问题：Givenacollectionofdistinctnumbers,returnallpossiblepermutations.Forexample,[1,2,3]havethefollowingpermutations:[[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]]大意：给出一个不同数字的集合，返回所有可能的排列。比如：[1,2,3]有下
Cloudox_·2017-04-06 09:07

LeetCode笔记：328. Odd Even Linked List

问题Givenasinglylinkedlist,groupalloddnodestogetherfollowedbytheevennodes.Pleasenoteherewearetalkingaboutthenodenumberandnotthevalueinthenodes.Youshouldtrytodoitinplace.TheprogramshouldruninO(1)spacecom
Cloudox_·2017-03-30 10:04

LeetCode笔记：423. Reconstruct Original Digits from English

问题：Givenanon-emptystringcontaininganout-of-orderEnglishrepresentationofdigits0-9,outputthedigitsinascendingorder.Note:1、InputcontainsonlylowercaseEnglishletters.2、Inputisguaranteedtobevalidandcanbetra
Cloudox_·2017-03-29 10:32

LeetCode笔记：423. Reconstruct Original Digits from English

问题：Givenanon-emptystringcontaininganout-of-orderEnglishrepresentationofdigits0-9,outputthedigitsinascendingorder.Note:1、InputcontainsonlylowercaseEnglishletters.2、Inputisguaranteedtobevalidandcanbetra
Cloudox_·2017-03-29 10:32

LeetCode笔记：318. Maximum Product of Word Lengths

问题：Givenastringarraywords,findthemaximumvalueoflength(word[i])*length(word[j])wherethetwowordsdonotsharecommonletters.Youmayassumethateachwordwillcontainonlylowercaseletters.Ifnosuchtwowordsexist,retu
Cloudox_·2017-03-28 09:41

LeetCode笔记：503. Next Greater Element II

问题：Givenacirculararray(thenextelementofthelastelementisthefirstelementofthearray),printtheNextGreaterNumberforeveryelement.TheNextGreaterNumberofanumberxisthefirstgreaternumbertoitstraversing-ordernex
Cloudox_·2017-03-17 09:18

LeetCode笔记：503. Next Greater Element II

问题：Givenacirculararray(thenextelementofthelastelementisthefirstelementofthearray),printtheNextGreaterNumberforeveryelement.TheNextGreaterNumberofanumberxisthefirstgreaternumbertoitstraversing-ordernex
Cloudox_·2017-03-17 09:18

LeetCode笔记：508. Most Frequent Subtree Sum

问题：Giventherootofatree,youareaskedtofindthemostfrequentsubtreesum.Thesubtreesumofanodeisdefinedasthesumofallthenodevaluesformedbythesubtreerootedatthatnode(includingthenodeitself).Sowhatisthemostfrequ
Cloudox_·2017-03-15 10:31

LeetCode笔记：508. Most Frequent Subtree Sum

问题：Giventherootofatree,youareaskedtofindthemostfrequentsubtreesum.Thesubtreesumofanodeisdefinedasthesumofallthenodevaluesformedbythesubtreerootedatthatnode(includingthenodeitself).Sowhatisthemostfrequ
Cloudox_·2017-03-15 10:31

LeetCode笔记：526. Beautiful Arrangement

问题：SupposeyouhaveNintegersfrom1toN.WedefineabeautifularrangementasanarraythatisconstructedbytheseNnumberssuccessfullyifoneofthefollowingistruefortheithposition(1≤i≤N)inthisarray:Thenumberattheithposit
Cloudox_·2017-03-14 09:27

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

问题：Youneedtofindthelargestvalueineachrowofabinarytree.Example:Input:Output:[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：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，一行行分析过去。还记得我们在传送门：
Cloudox_·2017-03-13 14:00

LeetCode笔记：513. Find Bottom Left Tree Value

问题：Givenabinarytree,findtheleftmostvalueinthelastrowofthetree.Example1:Input:Output:1Example2:Input:Output:7Note:Youmayassumethetree(i.e.,thegivenrootnode)isnotNULL.大意：给出一个二叉树，找到树最下一行的最左边的节点值。例1：输入：输出
Cloudox_·2017-03-08 09:38

LeetCode笔记：513. Find Bottom Left Tree Value

问题：Givenabinarytree,findtheleftmostvalueinthelastrowofthetree.Example1:Input:Output:1Example2:Input:Output:7Note:Youmayassumethetree(i.e.,thegivenrootnode)isnotNULL.大意：给出一个二叉树，找到树最下一行的最左边的节点值。例1：输入：输出
Cloudox_·2017-03-08 09:38

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_·2017-01-20 09:54

LeetCode笔记：392. Is Subsequence

问题：Givenastringsandastringt,checkifsissubsequenceoft.YoumayassumethatthereisonlylowercaseEnglishlettersinbothsandt.tispotentiallyaverylong(length~=500,000)string,andsisashortstring(=1B,andyouwanttoche
Cloudox_·2017-01-17 14:25

LeetCode笔记：343. Integer Break

问题：Givenapositiveintegern,breakitintothesumofatleasttwopositiveintegersandmaximizetheproductofthoseintegers.Returnthemaximumproductyoucanget.Forexample,givenn=2,return1(2=1+1);givenn=10,return36(10=3+
Cloudox_·2017-01-16 15:09

LeetCode笔记：482. License Key Formatting

问题：NowyouaregivenastringS,whichrepresentsasoftwarelicensekeywhichwewouldliketoformat.ThestringSiscomposedofalphanumericalcharactersanddashes.Thedashessplitthealphanumericalcharacterswithinthestringint
Cloudox_·2017-01-13 09:01

LeetCode笔记：481. Magical String

问题：AmagicalstringSconsistsofonly‘1’and‘2’andobeysthefollowingrules:ThestringSismagicalbecauseconcatenatingthenumberofcontiguousoccurrencesofcharacters‘1’and‘2’generatesthestringSitself.Thefirstfewelem
Cloudox_·2017-01-12 10:13

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_·2017-01-06 09:13

LeetCode笔记：442. Find All Duplicates in an Array

问题：Givenanarrayofintegers,1≤a[i]≤n(n=sizeofarray),someelementsappeartwiceandothersappearonce.Findalltheelementsthatappeartwiceinthisarray.CouldyoudoitwithoutextraspaceandinO(n)runtime?Example:Input:[4
Cloudox_·2017-01-05 09:43
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