LeetCode题解

LeetCode题解(1)--Two Sum

原题:　　　　　　　　　　　　　　　　　　　　　　　　　　https://leetcode.com/problems/two-sum/   Given an array of integers, find two numbers such that they add up to a specific target number. The function twoSum should
·2015-11-02 17:33

[LeetCode] 4Sum

算法渣，现实基本都参考或者完全拷贝[戴方勤([email protected])]大神的leetcode题解，此处仅作刷题记录。
·2015-11-02 17:23

[LeetCode] 3Sum Closest

算法渣，现实基本都参考或者完全拷贝[戴方勤([email protected])]大神的leetcode题解，此处仅作刷题记录。
·2015-11-02 17:21

[LeetCode] 3Sum

算法渣，现实基本都参考或者完全拷贝[戴方勤([email protected])]大神的leetcode题解，此处仅作刷题记录。
·2015-11-02 17:21

[LeetCode] Two Sum

算法渣，现实基本都参考或者完全拷贝[戴方勤([email protected])]大神的leetcode题解，此处仅作刷题记录。
·2015-11-02 17:20

[LeetCode题解]: Sort Colors

前言   【LeetCode 题解】系列传送门：  http://www.cnblogs.com/double-win/category/573499.html   1.题目描述 Given an array with n objects colored red, white or blue, sort them so that objects of th
·2015-11-01 11:57

LeetCode题解(20)--Valid Parentheses

https://leetcode.com/problems/valid-parentheses/ 原题： Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string i
·2015-10-31 16:01

LeetCode题解(19)--Remove Nth Node From End of List

                https://leetcode.com/problems/remove-nth-node-from-end-of-list/ 原题： Given a linked list, remove the nth node from the end of
·2015-10-31 16:00

LeetCode题解(14)--Longest Common Prefix

https://leetcode.com/problems/longest-common-prefix/ 原题： Write a function to find the longest common prefix string amongst an array of strings. 思路： 简单，直接遍历查找即可。 AC代码： 1 class Solution { 2 pu
·2015-10-31 16:59

LeetCode题解(12)--Integer to Roman

https://leetcode.com/problems/integer-to-roman/ 原题： Given an integer, convert it to a roman numeral. Input is guaranteed to be within the range from 1 to 3999.   思路： 掌握罗马数字规则并实现即可。（具体规则见&nb
·2015-10-31 16:58

LeetCode题解——Kth Largest Element in an Array

Findthe kthlargestelementinanunsortedarray.Notethatitisthekthlargestelementinthesortedorder,notthekthdistinctelement.Forexample,Given [3,2,1,5,6,4] andk=2,return5.Note: Youmayassumekisalwaysvalid,1≤k≤
u010025211·2015-10-27 15:00

LeetCode题解——Number of Digit One

Givenanintegern,countthetotalnumberofdigit1appearinginallnon-negativeintegerslessthanorequalton.Forexample:Givenn=13,Return6,becausedigit1occurredinthefollowingnumbers:1,10,11,12,13.解题思路：想法一：从一到n依次计算每
u010025211·2015-10-27 14:00

LeetCode题解——Factorial Trailing Zeroes

Givenaninteger n,returnthenumberoftrailingzeroesin n!.Note: Yoursolutionshouldbeinlogarithmictimecomplexity.出现0的情况是，出现5和2的倍数。[n/k]代表1~n中能被k整除的个数，而能被2整除的个数多余能被5整除的个数，故只要知道能被5整除的个数即可。那么怎样计算n!的质因子中所有5的个数
u010025211·2015-10-27 11:00

LeetCode题解——Count Primes

escription:Countthenumberofprimenumberslessthananon-negativenumber, n.Hint:Let'sstartwitha isPrime function.Todetermineifanumberisprime,weneedtocheckifitisnotdivisiblebyanynumberlessthan n.Theruntimec
u010025211·2015-10-26 21:00

LeetCode题解——Ugly Number II

Writeaprogramtofindthe n-thuglynumber.Uglynumbersarepositivenumberswhoseprimefactorsonlyinclude 2,3,5.Forexample, 1,2,3,4,5,6,8,9,10,12 isthesequenceofthefirst 10 uglynumbers.Notethat 1 istypicallytre
u010025211·2015-10-22 19:00

LeetCode题解——Happy Number

Writeanalgorithmtodetermineifanumberis"happy".Ahappynumberisanumberdefinedbythefollowingprocess:Startingwithanypositiveinteger,replacethenumberbythesumofthesquaresofitsdigits,andrepeattheprocessuntilt
u010025211·2015-10-22 19:00

LeetCode题解——Multiply Strings

Giventwonumbersrepresentedasstrings,returnmultiplicationofthenumbersasastring.Note:Thenumberscanbearbitrarilylargeandarenon-negative.此题可以用来求两个大数相乘。思路：逐位相乘处理进位法。假设两个字符串a和b以及保存结果的字符串c.对每个i，j;将a[i]*b[j]的
u010025211·2015-10-16 16:00

LeetCode题解——Plus One

Givenanon-negativenumberrepresentedasanarrayofdigits,plusonetothenumber.Thedigitsarestoredsuchthatthemostsignificantdigitisattheheadofthelist.思路：从尾到头逐位遍历字符串，如果当前字符不为‘9’，那么直接将此字符加1，返回。如果当前字符为‘9’，那么将此字符
u010025211·2015-10-16 14:00

LeetCode题解——Add Binary

Giventwobinarystrings,returntheirsum(alsoabinarystring).Forexample,a= "11"b= "1"Return "100".思路：最直接的想法，从最后一位开始，逐位运算。classSolution{ public: //特殊输入：空字符串，10+1;11+11,1111+11,1011+11; stringaddBinary(strin
u010025211·2015-10-16 14:00

LeetCode题解：Sum Root to Leaf Numbers

Givenabinarytreecontainingdigitsfrom0-9only,eachroot-to-leafpathcouldrepresentanumber.Anexampleistheroot-to-leafpath1->2->3whichrepresentsthenumber123.Findthetotalsumofallroot-to-leafnumbers.Forexampl
u012403246·2015-10-02 21:00

LeetCode题解：Word Ladder

Giventwowords(beginWordandendWord),andadictionary’swordlist,findthelengthofshortesttransformationsequencefrombeginWordtoendWord,suchthat:OnlyonelettercanbechangedatatimeEachintermediatewordmustexistin
u012403246·2015-10-02 21:00

LeetCode题解：Best Time to Buy and Sell Stock II

Sayyouhaveanarrayforwhichtheithelementisthepriceofagivenstockondayi.Designanalgorithmtofindthemaximumprofit.Youmaycompleteasmanytransactionsasyoulike(ie,buyoneandselloneshareofthestockmultipletimes).H
u012403246·2015-10-02 21:00

LeetCode题解：Best Time to Buy and Sell Stock

Sayyouhaveanarrayforwhichtheithelementisthepriceofagivenstockondayi.Ifyouwereonlypermittedtocompleteatmostonetransaction(ie,buyoneandselloneshareofthestock),designanalgorithmtofindthemaximumprofit.题意：
u012403246·2015-10-02 21:00

LeetCode题解：Triangle

Givenatriangle,findtheminimumpathsumfromtoptobottom.Eachstepyoumaymovetoadjacentnumbersontherowbelow.Forexample,giventhefollowingtriangle[[2],[3,4],[6,5,7],[4,1,8,3]]Theminimumpathsumfromtoptobottomis
u012403246·2015-10-02 21:00

LeetCode题解：Populating Next Right Pointers in Each Node

GivenabinarytreestructTreeLinkNode{ TreeLinkNode*left; TreeLinkNode*right; TreeLinkNode*next; } Populateeachnextpointertopointtoitsnextrightnode.Ifthereisnonextrightnode,thenextpointershouldbesettoNUL
u012403246·2015-10-02 21:00

LeetCode题解：Flatten Binary Tree to Linked List

Givenabinarytree,flattenittoalinkedlistin-place.Forexample,Given1 /\ 25 /\\ 346 Theflattenedtreeshouldlooklike:1\2\3\4\5\6题意：看不懂……弄了几棵树跑结果发现是先序遍历解决思路：先序遍历代码：publicclassSolution{ publicvoidflatten(Tree
u012403246·2015-10-02 20:00

LeetCode题解：Path Sum II

Givenabinarytreeandasum,findallroot-to-leafpathswhereeachpath’ssumequalsthegivensum.Forexample:Giventhebelowbinarytreeandsum=22,5/\48//\11134/\/\7251return[[5,4,11,2],[5,8,4,5]]题意：给定一棵二叉树，找到所有根->叶子结点的
u012403246·2015-10-02 20:00

LeetCode题解：Convert Sorted List to Binary Search Tree

Givenasinglylinkedlistwhereelementsaresortedinascendingorder,convertittoaheightbalancedBST.题意：给定一个升序排列的单链表，转换为二叉搜索树解决思路：同样是二分……代码：publicclassSolution{ privateListNodenode; publicTreeNodesortedListToB
u012403246·2015-10-02 20:00

LeetCode题解：Convert Sorted Array to Binary Search Tree

Givenanarraywhereelementsaresortedinascendingorder,convertittoaheightbalancedBST.题意：给定一个升序数组，将它转换为二叉搜索树解决思路：二分……代码：publicclassSolution{ publicTreeNodesortedArrayToBST(int[]num){ if(num.length==0){ ret
u012403246·2015-10-02 20:00

LeetCode题解：Construct Binary Tree from Inorder and Postorder Traversal

Giveninorderandpostordertraversalofatree,constructthebinarytree.Note:Youmayassumethatduplicatesdonotexistinthetree.题解：通过中序遍历和后序遍历还原二叉树解决思路：首先要明确一点，对于后序遍历的结果，如果一个元素所在的位置为i，若在中序遍历的i-1位置的元素为该元素的根结点，说明该元素
u012403246·2015-10-02 20:00

LeetCode题解：Construct Binary Tree from Preorder and Inorder Traversal

Givenpreorderandinordertraversalofatree,constructthebinarytree.Note:Youmayassumethatduplicatesdonotexistinthetree.题意：给定一棵树的前序遍历和中序遍历，还原二叉树解决思路：我们可以知道的是，前序遍历的第一个结点就是根节点，而且对于中序遍历，每一个根节点的左边是其左子树，右边是其右子树。
u012403246·2015-10-02 20:00

LeetCode题解：Binary Tree Zigzag Level Order Traversal

Givenabinarytree,returnthezigzaglevelordertraversalofitsnodes’values.(ie,fromlefttoright,thenrighttoleftforthenextlevelandalternatebetween).Forexample:Givenbinarytree{3,9,20,#,#,15,7},3/\920/\157retur
u012403246·2015-10-02 20:00

LeetCode题解：Validate Binary Search Tree

Givenabinarytree,determineifitisavalidbinarysearchtree(BST).AssumeaBSTisdefinedasfollows:Theleftsubtreeofanodecontainsonlynodeswithkeyslessthanthenode’skey.Therightsubtreeofanodecontainsonlynodeswithk
u012403246·2015-10-02 20:00

LeetCode题解：Unique Binary Search Trees II

Givenn,generateallstructurallyuniqueBST’s(binarysearchtrees)thatstorevalues1…n.Forexample,Givenn=3,yourprogramshouldreturnall5uniqueBST’sshownbelow.13321\///\\321132//\\2123题意：给定n，求出结点取值在1->n的二叉搜索树所有表
u012403246·2015-10-02 20:00

LeetCode题解：Unique Binary Search Trees

Givenn,howmanystructurallyuniqueBST’s(binarysearchtrees)thatstorevalues1…n?Forexample,Givenn=3,thereareatotalof5uniqueBST’s.13321\///\\321132//\\2123题意：给定一个整数n代表二叉搜索树所能存储的最大整数，树中元素大小为1->n。在此情况下，求出二叉搜索
u012403246·2015-10-02 19:00

LeetCode题解：Binary Tree Inorder Traversal

Givenabinarytree,returntheinordertraversalofitsnodes’values.Forexample:Givenbinarytree{1,#,2,3},1\2/3return[1,3,2].题意：中序遍历二叉树解决思路：”左根右“的递归或者通过栈完成的迭代代码：publicclassSolution{ publicListinorderTraversal(T
u012403246·2015-10-02 19:00

LeetCode题解：Restore IP Addresses

Givenastringcontainingonlydigits,restoreitbyreturningallpossiblevalidIPaddresscombinations.Forexample:Given“25525511135”,return[“255.255.11.135”,“255.255.111.35”].(Orderdoesnotmatter)题意：给定一个字符串，判断其代表的
u012403246·2015-10-02 19:00

LeetCode题解：Reverse Linked List II

Reversealinkedlistfrompositionmton.Doitin-placeandinone-pass.Forexample:Given1->2->3->4->5->NULL,m=2andn=4,return1->4->3->2->5->NULL.Note:Givenm,nsatisfythefollowingcondition:1≤m≤n≤lengthoflist.题意：给定整
u012403246·2015-10-02 19:00

LeetCode题解：Decode Ways

AmessagecontaininglettersfromA-Zisbeingencodedtonumbersusingthefollowingmapping:‘A’->1‘B’->2…‘Z’->26Givenanencodedmessagecontainingdigits,determinethetotalnumberofwaystodecodeit.Forexample,Givenencode
u012403246·2015-10-02 19:00

LeetCode题解——Convert Sorted Array to Binary Search Tree

Givenanarraywhereelementsaresortedinascendingorder,convertittoaheightbalancedBST./** *Definitionforabinarytreenode. *structTreeNode{ *intval; *TreeNode*left; *TreeNode*right; *TreeNode(intx):val(x),le
u010025211·2015-09-30 16:00

LeetCode题解——Convert Sorted List to Binary Search Tree

Givenasinglylinkedlistwhereelementsaresortedinascendingorder,convertittoaheightbalancedBST.分析:要求最后得到一颗平衡二叉树，那么链表的中间节点就是二叉树的根节点，中间节点左边就是二叉树的左子树，中间节点右边就是二叉树的右子树首先找到链表的中间节点作为BST的根节点，根节点的左子树是以中间节点左边的节点建立的
u010025211·2015-09-30 16:00

LeetCode题解——Implement Queue using Stacks

Implementthefollowingoperationsofaqueueusingstacks.push(x)--Pushelementxtothebackofqueue.pop()--Removestheelementfrominfrontofqueue.peek()--Getthefrontelement.empty()--Returnwhetherthequeueisempty.Not
u010025211·2015-09-29 15:00

LeetCode题解——Implement Stack using Queues

Implementthefollowingoperationsofastackusingqueues.push(x)--Pushelementxontostack.pop()--Removestheelementontopofthestack.top()--Getthetopelement.empty()--Returnwhetherthestackisempty.Notes:Youmustuse
u010025211·2015-09-29 15:00

LeetCode题解——Add Digits

Givenanon-negativeinteger num,repeatedlyaddallitsdigitsuntiltheresulthasonlyonedigit.Forexample:Given num=38,theprocessislike: 3+8=11, 1+1=2.Since 2 hasonlyonedigit,returnit.Followup:Couldyoudoitwitho
u010025211·2015-09-29 11:00

LeetCode题解——Linked List Cycle II

explannationfrom:http://stackoverflow.com/questions/2936213/explain-how-finding-cycle-start-node-in-cycle-linked-list-workLetmetrytoclarifythecycledetectionalgorithmthatisprovidedathttp://en.wikipedia
u010025211·2015-09-25 11:00

LeetCode题解——Linked List Cycle

Givenalinkedlist,determineifithasacycleinit.Followup:Canyousolveitwithoutusingextraspace?/** *Definitionforsingly-linkedlist. *structListNode{ *intval; *ListNode*next; *ListNode(intx):val(x),next(NULL
u010025211·2015-09-25 10:00

LeetCode题解——Intersection of Two Linked Lists

Writeaprogramtofindthenodeatwhichtheintersectionoftwosinglylinkedlistsbegins.Forexample,thefollowingtwolinkedlists:A:a1→a2 ↘ c1→c2→c3 ↗ B:b1→b2→b3 begintointersectatnodec1.Notes:Ifthetwolinkedlistshav
u010025211·2015-09-25 09:00

LeetCode题解——Rotate Array

Rotateanarrayof n elementstotherightby k steps.Forexample,with n =7and k =3,thearray [1,2,3,4,5,6,7] isrotatedto [5,6,7,1,2,3,4].Note:Trytocomeupasmanysolutionsasyoucan,thereareatleast3differentwaysto
u010025211·2015-09-23 14:00

LeetCode题解：Subsets II

Givenacollectionofintegersthatmightcontainduplicates,nums,returnallpossiblesubsets.Note:Elementsinasubsetmustbeinnon-descendingorder.Thesolutionsetmustnotcontainduplicatesubsets.Forexample,Ifnums=[1,2
u012403246·2015-09-06 21:00

LeetCode题解：Subsets

Givenasetofdistinctintegers,nums,returnallpossiblesubsets.Note:Elementsinasubsetmustbeinnon-descendingorder.Thesolutionsetmustnotcontainduplicatesubsets.Forexample,Ifnums=[1,2,3],asolutionis:[[3],[1],
u012403246·2015-09-06 21:00
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