d1leet1:两数之和https://leetcode-cn.com/problems/two-sum给定nums=[2,7,11,15],target=9因为nums[0]+nums[1]=2+7=9所以返回[0,1]【hashmap存储】classSolution:deftwoSum(self,nums:List[int],target:int)->List[int]:#边界值判断ifnot

121.买卖股票的最佳时机*-easy还是太菜，想了很久用双指针来记录最小值和最大利润，每进来一个数就要比较是否为最小数，并且比较此时卖出是否比之前卖出赚的更多//14.57//15.25classSolution{public:intmaxProfit(vector&prices){if(prices.size()sum){sum=prices[i]-small;}if(small>prices

问题：Givenacollectionofintervals,findtheminimumnumberofintervalsyouneedtoremovetomaketherestoftheintervalsnon-overlapping.Note:1、Youmayassumetheinterval'sendpointisalwaysbiggerthanitsstartpoint.2、Interv

问题（Easy）：Aself-dividingnumberisanumberthatisdivisiblebyeverydigititcontains.Forexample,128isaself-dividingnumberbecause128%1==0,128%2==0,and128%8==0.Also,aself-dividingnumberisnotallowedtocontainthedi

题目：Givenanarrayofintegers,findifthearraycontainsanyduplicates.Yourfunctionshouldreturntrueifanyvalueappearsatleasttwiceinthearray,anditshouldreturnfalseifeveryelementisdistinct.大意：给出一个int型的数组，判断数组是否包含

问题（Easy）：Youaregivenamapinformofatwo-dimensionalintegergridwhere1representslandand0representswater.Gridcellsareconnectedhorizontally/vertically(notdiagonally).Thegridiscompletelysurroundedbywater,andt

问题（Easy）：Givenanm*nmatrixMinitializedwithall0'sandseveralupdateoperations.Operationsarerepresentedbya2Darray,andeachoperationisrepresentedbyanarraywithtwopositiveintegersaandb,whichmeansM[i][j]shouldb

问题：NowyouaregivenastringS,whichrepresentsasoftwarelicensekeywhichwewouldliketoformat.ThestringSiscomposedofalphanumericalcharactersanddashes.Thedashessplitthealphanumericalcharacterswithinthestringint

问题：Givenabinarytree,returnthepreordertraversalofitsnodes'values.Forexample:Givenbinarytree{1,#,2,3},image.pngreturn[1,2,3].Note:Recursivesolutionistrivial,couldyoudoititeratively?大意：给出一个二叉树，返回节点值的前序遍历

问题（Easy）：GivenaListofwords,returnthewordsthatcanbetypedusinglettersofalphabetononlyonerow'sofAmericankeyboardliketheimagebelow.Example1:Input:["Hello","Alaska","Dad","Peace"]Output:["Alaska","Dad"]Not

问题（Easy）：Youaregiventwoarrays(withoutduplicates)nums1andnums2wherenums1’selementsaresubsetofnums2.Findallthenextgreaternumbersfornums1'selementsinthecorrespondingplacesofnums2.TheNextGreaterNumberofan

问题（Easy）：Givenabinaryarray,findthemaximumnumberofconsecutive1sinthisarray.Example1:Input:[1,1,0,1,1,1]Output:3Explanation:Thefirsttwodigitsorthelastthreedigitsareconsecutive1s.Themaximumnumberofconsec

问题：Calculatethesumoftwointegersaandb,butyouarenotallowedtousetheoperator+and-.Example:Givena=1andb=2,return3.大意：计算a和b两个整数的和，但是不能用+或-运算符。比如：给出a=1和b=2，返回3.思路：这道题乍看之下很简单，计算两个数之和嘛，但问题在于不能直接使用加号和减号，这就尴尬了，不

动态规划最优子结构：问题的最优解由相关子问题的最优解组合而成，而这些子问题可以独立求解。即一个问题的最优解包含其子问题的最优解。独立求解的理解：如算法导论P218中所说，要保证分解后得到的子问题之间可以独立求解，也即同一分解中不同子问题所用资源之间没有交集动态规划与分治动态规划与分治法很相似，都是通过组合子问题的解来解原问题，但是分治法的子问题之间是不相交的，没有公共子子问题，比如归并排序，每一次

问题：Implementthefollowingoperationsofaqueueusingstacks.push(x)--Pushelementxtothebackofqueue.pop()--Removestheelementfrominfrontofqueue.peek()--Getthefrontelement.empty()--Returnwhetherthequeueisempty.

问题：Sayyouhaveanarrayforwhichtheithelementisthepriceofagivenstockondayi.Ifyouwereonlypermittedtocompleteatmostonetransaction(ie,buyoneandselloneshareofthestock),designanalgorithmtofindthemaximumprofit.

问题：Givenalinkedlist,removethenthnodefromtheendoflistandreturnitshead.Forexample,Givenlinkedlist:1->2->3->4->5,andn=2.Afterremovingthesecondnodefromtheend,thelinkedlistbecomes1->2->3->5.Note:Givennwill

问题：Writeanalgorithmtodetermineifanumberis"happy".Ahappynumberisanumberdefinedbythefollowingprocess:Startingwithanypositiveinteger,replacethenumberbythesumofthesquaresofitsdigits,andrepeattheprocessunt

问题（Easy）:Giventwobinarytreesandimaginethatwhenyouputoneofthemtocovertheother,somenodesofthetwotreesareoverlappedwhiletheothersarenot.Youneedtomergethemintoanewbinarytree.Themergeruleisthatiftwonodesov

问题：SupposeyouhaveNintegersfrom1toN.WedefineabeautifularrangementasanarraythatisconstructedbytheseNnumberssuccessfullyifoneofthefollowingistruefortheithposition(1≤i≤N)inthisarray:Thenumberattheithposit

问题：Findthetotalareacoveredbytworectilinearrectanglesina2Dplane.Eachrectangleisdefinedbyitsbottomleftcornerandtoprightcornerasshowninthefigure.image.pngAssumethatthetotalareaisneverbeyondthemaximumposs

问题：Writeaprogramtocheckwhetheragivennumberisanuglynumber.Uglynumbersarepositivenumberswhoseprimefactorsonlyinclude2,3,5.Forexample,6,8areuglywhile14isnotuglysinceitincludesanotherprimefactor7.Notethat

题目：Writeafunctiontodeleteanode(exceptthetail)inasinglylinkedlist,givenonlyaccesstothatnode.Supposedthelinkedlistis1->2->3->4andyouaregiventhethirdnodewithvalue3,thelinkedlistshouldbecome1->2->4afterca

问题：Implementthefollowingoperationsofastackusingqueues.push(x)--Pushelementxontostack.pop()--Removestheelementontopofthestack.top()--Getthetopelement.empty()--Returnwhetherthestackisempty.Notes:Youmust

问题：Givenanarbitraryransomnotestringandanotherstringcontaininglettersfromallthemagazines,writeafunctionthatwillreturntrueiftheransomnotecanbeconstructedfromthemagazines;otherwise,itwillreturnfalse.Each

问题：Givenapositiveintegern,breakitintothesumofatleasttwopositiveintegersandmaximizetheproductofthoseintegers.Returnthemaximumproductyoucanget.Forexample,givenn=2,return1(2=1+1);givenn=10,return36(10=3+

问题：YouareplayingthefollowingNimGamewithyourfriend:Thereisaheapofstonesonthetable,eachtimeoneofyoutaketurnstoremove1to3stones.Theonewhoremovesthelaststonewillbethewinner.Youwilltakethefirstturntoremove

题目：Reverseasinglylinkedlist.大意：反转一个简单链表。思路：题目的意思就是给出一个链表，本来是从头指向尾的，现在要你做成从尾指向头，并且返回原来的尾，现在的头。这个肯定是要用递归或者迭代来做。只要屡清楚过程，会比较绕。大体的流程就是，把下一个节点的next指向自己，一个个迭代、递归下去，最后返回最后的原来的尾节点他山之石：这里给出Discuss中最火的方法。迭代实现：pu

问题：Findthenthdigitoftheinfiniteintegersequence1,2,3,4,5,6,7,8,9,10,11,...Note:nispositiveandwillfitwithintherangeofa32-bitsignedinteger(nreduce+num*i){lastNum=lastNum+num;reduce=reduce+num*i;num=num*1

题目：Giventwobinarytrees,writeafunctiontocheckiftheyareequalornot.Twobinarytreesareconsideredequaliftheyarestructurallyidenticalandthenodeshavethesamevalue.大意：给出两个二叉树，写一个函数来检查两者是否相等。所谓相等，是指他们结构相同且节点有同样的

题目：Givenanarrayofsizen,findthemajorityelement.Themajorityelementistheelementthatappearsmorethan⌊n/2⌋times.Youmayassumethatthearrayisnon-emptyandthemajorityelementalwaysexistinthearray.大意：给出一个尺寸为n的数组，找

问题：Supposeyouhavearandomlistofpeoplestandinginaqueue.Eachpersonisdescribedbyapairofintegers(h,k),wherehistheheightofthepersonandkisthenumberofpeopleinfrontofthispersonwhohaveaheightgreaterthanorequalt

问题：GivennumRows,generatethefirstnumRowsofPascal'striangle.Forexample,givennumRows=5,Return[[1],[1,1],[1,2,1],[1,3,3,1],[1,4,6,4,1]]大意：给出一个行数，生出对应行数的杨辉三角形。比如，给出行数=5。返回[[1],[1,1],[1,2,1],[1,3,3,1],[1,4,

问题：Giventwobinarystrings,returntheirsum(alsoabinarystring).Forexample,a="11"b="1"Return"100".大意：给出两个二进制字符串，返回它们的和（同样是二进制字符串）。例子：a="11"b="1"返回"100".思路：这其实就是一个模拟二进制加法的问题。如果某一位两个数都是0，结果的这一位也为0，有一个1就是1，如果

问题：Givenanxnmatrixwhereeachoftherowsandcolumnsaresortedinascendingorder,findthekthsmallestelementinthematrix.Notethatitisthekthsmallestelementinthesortedorder,notthekthdistinctelement.Example:image.pn

问题：Giventherootofatree,youareaskedtofindthemostfrequentsubtreesum.Thesubtreesumofanodeisdefinedasthesumofallthenodevaluesformedbythesubtreerootedatthatnode(includingthenodeitself).Sowhatisthemostfrequ

问题：GivenamatrixofMxNelements(Mrows,Ncolumns),returnallelementsofthematrixindiagonalorderasshowninthebelowimage.Example:Input:[[1,2,3],[4,5,6],[7,8,9]]Output:[1,2,4,7,5,3,6,8,9]Explanation:image.pngNot

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

问题：Thegraycodeisabinarynumeralsystemwheretwosuccessivevaluesdifferinonlyonebit.Givenanon-negativeintegernrepresentingthetotalnumberofbitsinthecode,printthesequenceofgraycode.Agraycodesequencemustbegin

问题：Assumeyouareanawesomeparentandwanttogiveyourchildrensomecookies.But,youshouldgiveeachchildatmostonecookie.Eachchildihasagreedfactorgi,whichistheminimumsizeofacookiethatthechildwillbecontentwith;and

问题：Givenastringwhichconsistsoflowercaseoruppercaseletters,findthelengthofthelongestpalindromesthatcanbebuiltwiththoseletters.Thisiscasesensitive,forexample"Aa"isnotconsideredapalindromehere.Note:Assum

问题：Therearenbulbsthatareinitiallyoff.Youfirstturnonallthebulbs.Then,youturnoffeverysecondbulb.Onthethirdround,youtoggleeverythirdbulb(turningonifit'sofforturningoffifit'son).Fortheithround,youtoggleev

问题：Asequenceofnumberiscalledarithmeticifitconsistsofatleastthreeelementsandifthedifferencebetweenanytwoconsecutiveelementsisthesame.Forexample,thesearearithmeticsequence:1,3,5,7,97,7,7,73,-1,-5,-9Thef

问题：Writeaprogramtofindthenodeatwhichtheintersectionoftwosinglylinkedlistsbegins.Forexample,thefollowingtwolinkedlists:image.pngbegintointersectatnodec1.Notes:Ifthetwolinkedlistshavenointersectionatall

问题：Givenanon-negativeintegernum,repeatedlyaddallitsdigitsuntiltheresulthasonlyonedigit.Forexample:Givennum=38,theprocessislike:3+8=11,1+1=2.Since2hasonlyonedigit,returnit.Followup:Couldyoudoitwithouta

问题：WeareplayingtheGuessGame.Thegameisasfollows:Ipickanumberfrom1ton.YouhavetoguesswhichnumberIpicked.Everytimeyouguesswrong,I'lltellyouwhetherthenumberishigherorlower.Youcallapre-definedAPIguess(intnu

问题（Easy）：Givenanarrayof2nintegers,yourtaskistogrouptheseintegersintonpairsofinteger,say(a1,b1),(a2,b2),...,(an,bn)whichmakessumofmin(ai,bi)forallifrom1tonaslargeaspossible.Example1:Input:[1,4,3,2]Outp

问题（Easy）：Givenanon-emptybinarytree,returntheaveragevalueofthenodesoneachlevelintheformofanarray.Example1:Input:Output:[3,14.5,11]Explanation:Theaveragevalueofnodesonlevel0is3,onlevel1is14.5,andonlevel

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

问题（Easy）：Givenastring,youneedtoreversetheorderofcharactersineachwordwithinasentencewhilestillpreservingwhitespaceandinitialwordorder.Example1:Input:"Let'stakeLeetCodecontest"Output:"s'teLekatedoCteeLt