leetCode笔记

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_·2016-03-26 14:00

LeetCode笔记：258.Add Digits

问题：Givenanon-negativeintegernum,repeatedlyaddallitsdigitsuntiltheresulthasonlyonedigit.Forexample:Givennum=38,theprocessislike:3+8=11,1+1=2.Since2hasonlyonedigit,returnit.Followup:Couldyoudoitwithouta
Cloudox_·2016-03-24 15:26

LeetCode笔记：258.Add Digits

问题：Givenanon-negativeintegernum,repeatedlyaddallitsdigitsuntiltheresulthasonlyonedigit.Forexample:Givennum=38,theprocessislike:3+8=11,1+1=2.Since2hasonlyonedigit,returnit.Followup:Couldyoudoitwithouta
Cloudox_·2016-03-24 15:00

LeetCode笔记：258.Add Digits

问题：Givenanon-negativeintegernum,repeatedlyaddallitsdigitsuntiltheresulthasonlyonedigit.Forexample:Givennum=38,theprocessislike:3+8=11,1+1=2.Since2hasonlyonedigit,returnit.Followup:Couldyoudoitwithouta
Cloudox_·2016-03-24 15:00

LeetCode笔记：292.Nim Game

问题：YouareplayingthefollowingNimGamewithyourfriend:Thereisaheapofstonesonthetable,eachtimeoneofyoutaketurnstoremove1to3stones.Theonewhoremovesthelaststonewillbethewinner.Youwilltakethefirstturntoremove
Cloudox_·2016-03-24 15:18

LeetCode笔记：292.Nim Game

问题：YouareplayingthefollowingNimGamewithyourfriend:Thereisaheapofstonesonthetable,eachtimeoneofyoutaketurnstoremove1to3stones.Theonewhoremovesthelaststonewillbethewinner.Youwilltakethefirstturntoremove
Cloudox_·2016-03-24 15:00

LeetCode笔记：292.Nim Game

问题：YouareplayingthefollowingNimGamewithyourfriend:Thereisaheapofstonesonthetable,eachtimeoneofyoutaketurnstoremove1to3stones.Theonewhoremovesthelaststonewillbethewinner.Youwilltakethefirstturntoremove
Cloudox_·2016-03-24 15:00

leetcode笔记：House Robber III

一.题目描述Thethiefhasfoundhimselfanewplaceforhisthieveryagain.Thereisonlyoneentrancetothisarea,calledthe“root.”Besidestheroot,eachhousehasoneandonlyoneparenthouse.Afteratour,thesmartthiefrealizedthat“allh
liyuefeilong·2016-03-14 20:00

leetcode笔记：Maximum Product of Word Lengths

一.题目描述Givenastringarraywords,findthemaximumvalueoflength(word[i])*length(word[j])wherethetwowordsdonotsharecommonletters.Youmayassumethateachwordwillcontainonlylowercaseletters.Ifnosuchtwowordsexist,r
liyuefeilong·2016-03-07 16:00

leetcode笔记：Bitwise AND of Numbers Range

一.题目描述Givenarange[m,n]where0100->4 7:111再来两个例子：范围[6,8]：6:0110 7:0111->0000->0 8:1000范围[8,10]：8:1000 9:1001->1000->4 10:1010现在可以总结出规律了，对于范围[m,n]，若n的最高有效位比m的最高有效位要高，则必然会出现像例子出现的情况，必然在范围内存在两个数，这两个数分别是对方的
liyuefeilong·2016-03-04 18:00

leetcode笔记：Rectangle Area

一.题目描述Findthetotalareacoveredbytworectilinearrectanglesina2Dplane.Eachrectangleisdefinedbyitsbottomleftcornerandtoprightcornerasshowninthefigure.Assumethatthetotalareaisneverbeyondthemaximumpossibleva
liyuefeilong·2016-02-29 17:00

leetcode笔记：Majority Element II

一.题目描述Givenanintegerarrayofsizen,findallelementsthatappearmorethan⌊n/3⌋times.ThealgorithmshouldruninlineartimeandinO(1)space.Hint:Howmanymajorityelementscoulditpossiblyhave?二.题目分析题目大意是，给定一个大小为n的整数数组，从
Herbert_Zero·2016-02-28 20:55

leetcode笔记：Majority Element II

一.题目描述Givenanintegerarrayofsizen,findallelementsthatappearmorethan⌊n/3⌋times.ThealgorithmshouldruninlineartimeandinO(1)space.Hint:Howmanymajorityelementscoulditpossiblyhave?二.题目分析题目大意是，给定一个大小为n的整数数组，从
liyuefeilong·2016-02-28 20:00

leetcode笔记：Range Sum Query 2D - Immutable

一.题目描述Givena2Dmatrixmatrix,findthesumoftheelementsinsidetherectangledefinedbyitsupperleftcorner(row1,col1)andlowerrightcorner(row2,col2).Theaboverectangle(withtheredborder)isdefinedby(row1,col1)=(2,1)
liyuefeilong·2016-02-28 18:00

leetcode笔记：Contains Duplicate III

一.题目描述Givenanarrayofintegers,findoutwhethertherearetwodistinctindicesiandjinthearraysuchthatthedifferencebetweennums[i]andnums[j]isatmosttandthedifferencebetweeniandjisatmostk.二.题目分析题目大意是，给定一个整数数组，判断其
liyuefeilong·2016-02-26 15:00

leetcode笔记--Summary Ranges

题目：难度（Easy）Givenasortedintegerarraywithoutduplicates,returnthesummaryofitsranges.Forexample,given[0,1,2,4,5,7],return["0->2","4->5","7"].Tags：ArraySimilarProblems：(M)MissingRanges分析：i指向一个range片段的起始元素，
u010366748·2016-02-25 15:00

leetcode笔记：Contains Duplicate II

一.题目描述Givenanarrayofintegersandanintegerk,findoutwhethertherearetwodistinctindicesiandjinthearraysuchthatnums[i]=nums[j]andthedifferencebetweeniandjisatmostk.二.题目分析题目的大意是，给定一个整数数组与一个整数k，当且仅当存在两个不同的下标i
liyuefeilong·2016-02-24 18:00

leetcode笔记--Reverse Words in a String

题目：难度（Medium）Givenaninputstring,reversethestringwordbyword.Forexample,Givens="theskyisblue",return"blueisskythe".Update(2015-02-12):ForCprogrammers:Trytosolveitin-placeinO(1)space.Clarification(声明):Wh
u010366748·2016-02-24 18:00

leetcode笔记--Simplify Path

题目：难度（Medium）Givenanabsolutepathforafile(Unix-style),simplifyit.Forexample,path="/home/",=>"/home"path="/a/./b/../../c/",=>"/c"CornerCases(极端条件):Didyouconsiderthecasewherepath="/../"?Inthiscase,yousho
u010366748·2016-02-24 18:00

leetcode笔记：Contains Duplicate

一.题目描述Givenanarrayofintegers,findifthearraycontainsanyduplicates.Yourfunctionshouldreturntrueifanyvalueappearsatleasttwiceinthearray,anditshouldreturnfalseifeveryelementisdistinct.二.题目分析题目的大意是，给定一个整数数
liyuefeilong·2016-02-24 18:00

leetcode笔记--Compare Version Numbers

题目：难度（Easy）Comparetwoversionnumbersversion1andversion2.Ifversion1>version2return1,ifversion1len(v2): length=len(v1) i=len(v2) whileiv2[i]: return1 elifv1[i]
u010366748·2016-02-24 16:00

leetcode笔记--Count and Say

题目：难度（Easy）Thecount-and-saysequenceisthesequenceofintegersbeginningasfollows:1,11,21,1211,111221,...1isreadoffas"one1"or11.11isreadoffas"two1s"or21.21isreadoffas"one2,thenone1"or1211.Givenanintegern,g
u010366748·2016-02-24 15:00

leetcode笔记--Length of Last Word

题目：难度（Easy）Givenastringsconsistsofupper/lower-casealphabetsandemptyspacecharacters'',returnthelengthoflastwordinthestring.Ifthelastworddoesnotexist,return0.Note:Awordisdefinedasacharactersequenceconsi
u010366748·2016-02-24 13:00

leetcode笔记：Find the Duplicate Number

一.题目描述Givenanarraynumscontainingn+1integerswhereeachintegerisbetween1andn(inclusive),provethatatleastoneduplicateelementmustexist.Assumethatthereisonlyoneduplicatenumber,findtheduplicateone.Note:Youmu
liyuefeilong·2016-02-22 23:00

leetcode笔记：Increasing Triplet Subsequence

一.题目描述Givenanunsortedarrayreturnwhetheranincreasingsubsequenceoflength3existsornotinthearray.Formallythefunctionshould:Returntrueifthereexistsi,j,ksuchthatarr[i]&nums){ intn=nums.size(); if(n<3)return
liyuefeilong·2016-02-22 17:00

leetcode笔记：Longest Increasing Path in a Matrix

一.题目描述Givenanintegermatrix,findthelengthofthelongestincreasingpath.Fromeachcell,youcaneithermovetofourdirections:left,right,upordown.YoumayNOTmovediagonallyormoveoutsideoftheboundary(i.e.wrap-aroundis
liyuefeilong·2016-02-21 23:00

leetcode笔记：Missing Number

一.题目描述Givenanarraycontainingndistinctnumberstakenfrom0,1,2,...,n,findtheonethatismissingfromthearray.Forexample,Givennums=[0,1,3]return2.Note:Youralgorithmshouldruninlinearruntimecomplexity.Couldyouim
liyuefeilong·2016-02-19 14:00

leetcode笔记：Super Ugly Number

一.题目描述Writeaprogramtofindthenthsuperuglynumber.Superuglynumbersarepositivenumberswhoseallprimefactorsareinthegivenprimelistprimesofsizek.Forexample,[1,2,4,7,8,13,14,16,19,26,28,32]isthesequenceofthefi
liyuefeilong·2016-02-18 22:00

leetcode笔记：Coin Change

一.题目描述Youaregivencoinsofdifferentdenominationsandatotalamountofmoneyamount.Writeafunctiontocomputethefewestnumberofcoinsthatyouneedtomakeupthatamount.Ifthatamountofmoneycannotbemadeupbyanycombinationo
liyuefeilong·2016-02-18 16:00

leetcode笔记：Game of Life

一.题目描述AccordingtotheWikipedia’sarticle:“TheGameofLife,alsoknownsimplyasLife,isacellularautomatondevisedbytheBritishmathematicianJohnHortonConwayin1970.”Givenaboardwithmbyncells,eachcellhasaninitialsta
liyuefeilong·2016-02-18 00:00

leetcode笔记：Word Pattern

一.题目描述Givenapatternandastringstr,findifstrfollowsthesamepattern.Herefollowmeansafullmatch,suchthatthereisabijectionbetweenaletterinpatternandanon-emptywordinstr.Examples:pattern="abba",str="dogcatcatd
liyuefeilong·2016-02-15 15:00

leetcode笔记：Wiggle Sort

一.题目描述Givenanunsortedarraynums,reorderitin-placesuchthatnums[0]=nums[2]=nums[2]=nums[i-1]当下标i是偶数时，nums[i]&nums){ if(nums.size()&nums){ if(nums.size()nums[i-1])) swap(nums[i],nums[i-1]); } } };四.小结后续有题
liyuefeilong·2016-02-14 14:00

leetcode笔记：Majority Element

一.题目描述Givenanarrayofsizen,findthemajorityelement.Themajorityelementistheelementthatappearsmorethan⌊n/2⌋times.Youmayassumethatthearrayisnon-emptyandthemajorityelementalwaysexistinthearray.二.题目分析题目说到，给定
liyuefeilong·2016-02-03 22:00

leetcode笔记：H-Index II

一.题目描述FollowupforH-Index:Whatifthecitationsarrayissortedinascendingorder?Couldyouoptimizeyouralgorithm?二.题目分析该题与H-Index一题的要求基本一致，只是多提供了一个条件，即传入的数组本身已经是升序排列的，因此实际上操作会方便许多，也无需再使用辅助数组。该题仍然可以使用H-Index方法从后
liyuefeilong·2016-02-01 16:00

leetcode笔记：H-Index

一.题目描述Givenanarrayofcitations(eachcitationisanon-negativeinteger)ofaresearcher,writeafunctiontocomputetheresearcher’sh-index.Accordingtothedefinitionofh-indexonWikipedia:“Ascientisthasindexhifhofhis/h
liyuefeilong·2016-02-01 15:00

leetcode笔记：Patching Array

一.题目描述Givenasortedpositiveintegerarraynumsandanintegern,add/patchelementstothearraysuchthatanynumberinrange[1,n]inclusivecanbeformedbythesumofsomeelementsinthearray.Returntheminimumnumberofpatchesrequ
liyuefeilong·2016-01-31 22:00

leetcode笔记：Perfect Squares

一.题目描述Givenapositiveintegern,findtheleastnumberofperfectsquarenumbers(forexample,1,4,9,16,...)whichsumton.Forexample,givenn=12,return3because12=4+4+4;givenn=13,return2because13=4+9.二.题目分析该题目的大意是，给出一个目
liyuefeilong·2016-01-29 23:00

leetcode笔记：Reverse Bits

一.题目描述Reversebitsofagiven32bitsunsignedinteger.Forexample,giveninput43261596(representedinbinaryas00000010100101000001111010011100),return964176192(representedinbinaryas0011100101111000001010010100000
liyuefeilong·2016-01-29 17:00

leetcode笔记：Count Primes

一.题目描述Countthenumberofprimenumberslessthananon-negativenumber,n.二.题目分析题目有很多tips，大意是算出2~n之间有多少个素数。若使用暴力法只会是超时，而正确的思路来自著名的埃拉托斯特尼筛法。简单来说，要得到自然数n以内的全部素数，必须把不大于sqrt(n)的所有素数的倍数剔除，剩下的就是素数。更多关于埃拉托斯特尼筛法，参照：htt
liyuefeilong·2016-01-27 23:00

leetcode笔记：Length of Last Word

一.题目描述Givenastringsconsistsofupper/lower-casealphabetsandemptyspacecharacters’‘,returnthelengthoflastwordinthestring.Ifthelastworddoesnotexist,return0.Note:Awordisdefinedasacharactersequenceconsistsof
liyuefeilong·2016-01-27 16:00

leetcode笔记：Word Break

一.题目描述Givenastringsandadictionaryofwordsdict,determineifscanbesegmentedintoaspace-separatedsequenceofoneormoredictionarywords.Forexample,givens="leetcode",dict=["leet","code"].Returntruebecause"leetco
liyuefeilong·2016-01-25 23:00

leetcode笔记：Move Zeroes

一.题目描述Givenanarraynums,writeafunctiontomoveall0'stotheendofitwhilemaintainingtherelativeorderofthenon-zeroelements.Forexample,givennums=[0,1,0,3,12],aftercallingyourfunction,numsshouldbe[1,3,12,0,0].N
liyuefeilong·2016-01-23 11:00

leetcode笔记：Range Sum Query - Mutable

一.题目描述Givenanintegerarraynums,findthesumoftheelementsbetweenindicesiandj(i≤j),inclusive.Theupdate(i,val)functionmodifiesnumsbyupdatingtheelementatindexitoval.Example:Givennums=[1,3,5]sumRange(0,2)->9
liyuefeilong·2016-01-21 01:00

leetcode笔记：Range Sum Query - Immutable

一.题目描述Givenanintegerarraynums,findthesumoftheelementsbetweenindicesiandj(i≤j),inclusive.Example:Givennums=[-2,0,3,-5,2,-1]sumRange(0,2)->1 sumRange(2,5)->-1 sumRange(0,5)->-3二.题目分析给定一个数组nums，求出下标i和j之间
liyuefeilong·2016-01-20 23:00

leetcode笔记：Divide Two Integers

一.题目描述Dividetwointegerswithoutusingmultiplication,divisionandmodoperator.Ifitisoverflow,returnMAX_INT.二.题目分析题目的意思简单明了，就是要求不使用乘法、除法和取余mod，输入两个整数，输出除法操作的结果。出去乘除法，剩下的只有加减法和位运算，这是不难想到的，而直接使用减法，对被除数逐次减去除数大
liyuefeilong·2016-01-20 22:00

leetcode笔记：ZigZag Conversion

一.题目描述Thestring“PAYPALISHIRING”iswritteninazigzagpatternonagivennumberofrowslikethis:(youmaywanttodisplaythispatterninafixedfontforbetterlegibility)PAHN APLSIIG YIRAndthenreadlinebyline:"PAHNAPLSIIGYI
liyuefeilong·2016-01-18 23:00

leetcode笔记：Find Median from Data Stream

一.题目描述Medianisthemiddlevalueinanorderedintegerlist.Ifthesizeofthelistiseven,thereisnomiddlevalue.Sothemedianisthemeanofthetwomiddlevalue.Examples:[2,3,4],themedianis3[2,3],themedianis(2+3)/2=2.5Design
liyuefeilong·2016-01-14 22:00

leetcode笔记：Bulls and Cows

一.题目描述YouareplayingthefollowingBullsandCowsgamewithyourfriend:Youwritedownanumberandaskyourfriendtoguesswhatthenumberis.Eachtimeyourfriendmakesaguess,youprovideahintthatindicateshowmanydigitsinsaidgue
liyuefeilong·2016-01-13 21:00

leetcode笔记：Bulb Switcher

一.题目描述Therearenbulbsthatareinitiallyoff.Youfirstturnonallthebulbs.Then,youturnoffeverysecondbulb.Onthethirdround,youtoggleeverythirdbulb(turningonifit’sofforturningoffifit’son).Forthenthround,youonlyt
liyuefeilong·2016-01-13 16:00

leetcode笔记：Integer to English Words

一.题目描述Convertanon-negativeintegertoitsenglishwordsrepresentation.Giveninputisguaranteedtobelessthan231-1.Forexample,123->"OneHundredTwentyThree" 12345->"TwelveThousandThreeHundredFortyFive" 1234567->"
liyuefeilong·2016-01-12 18:00
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