Leetcode题解

LeetCode题解——Basic Calculator

Theexpressionstringmaycontainopen ( andclosingparentheses ),theplus + orminussign -, non-negative integersandemptyspaces .Youmayassumethatthegivenexpressionisalwaysvalid.Someexamples:"1+1"=2 "2-1+2"=3
u010025211·2015-11-08 17:00

LeetCode题解——Different Ways to Add Parentheses

Givenastringofnumbersandoperators,returnallpossibleresultsfromcomputingallthedifferentpossiblewaystogroupnumbersandoperators.Thevalidoperatorsare+, - and *.Example1Input: "2-1-1".((2-1)-1)=0 (2-(1-1))
u010025211·2015-11-08 11:00

LeetCode题解——Unique Binary Search Trees II

Given n,generateallstructurallyunique BST's (binarysearchtrees)thatstorevalues1...n.Forexample,Given n =3,yourprogramshouldreturnall5uniqueBST'sshownbelow.13321 \///\\ 321132 //\\ 2123 想法一：递归，思想见Uniqu
u010025211·2015-11-07 22:00

LeetCode题解——Unique Binary Search Trees

题目：Given n,howmanystructurallyunique BST's (binarysearchtrees)thatstorevalues1...n?Forexample,Given n =3,thereareatotalof5uniqueBST's.13321 \///\\ 321132 //\\ 2123解题思路：Theproblemcanbesolvedinadynamicp
u010025211·2015-11-07 20:00

LeetCode题解——Symmetric Tree

题目：Givenabinarytree,checkwhetheritisamirrorofitself(ie,symmetricarounditscenter).Forexample,thisbinarytreeissymmetric:1 /\ 22 /\/\ 3443 Butthefollowingisnot:1 /\ 22 \\ 33 解题思路：(1)如果一个树是对称的，那么左子树和右子树的关
u010025211·2015-11-06 14:00

LeetCode题解——Copy List with Random Pointer

Alinkedlistisgivensuchthateachnodecontainsanadditionalrandompointerwhichcouldpointtoanynodeinthelistornull.Returnadeepcopyofthelist.Subscribe toseewhichcompaniesaskedthisquestionAsanoptimisedsolution,
u010025211·2015-11-03 21:00

LeetCode题解——Binary Search Tree Iterator

mplementaniteratoroverabinarysearchtree(BST).YouriteratorwillbeinitializedwiththerootnodeofaBST.Calling next() willreturnthenextsmallestnumberintheBST.Note: next() and hasNext() shouldruninaverageO(1)
u010025211·2015-11-03 18:00

LeetCode题解——Reverse Words in a String

Givenaninputstring,reversethestringwordbyword.Forexample,Givens="theskyisblue",return"blueisskythe".Trytosolveit in-place in O(1)space.Clarification:Whatconstitutesaword?Asequenceofnon-spacecharacters
u010025211·2015-11-03 17:00

LeetCode题解(13)--Roman to Integer

https://leetcode.com/problems/roman-to-integer/ 原题： Given a roman numeral, convert it to an integer. Input is guaranteed to be within the range from 1 to 3999.   思路： 关键是要搞清罗马数字规则。PS:不用考虑错误输
·2015-11-02 17:39

LeetCode题解(9)--Palindrome Number

Determine whether an integer is a palindrome. Do this without extra space.   思想: 先计算出这个整数的逆序数，然后比较它和原来的数每位是否都相同即可。另外要注意负数没有回文数，还应该考虑overflow一定不是回文数。   AC代码： 1 class Solution { 2 pub
·2015-11-02 17:38

LeetCode题解(7)--Reverse Integer

Reverse digits of an integer. Example1: x = 123, return 321Example2: x = -123, return -321     思想：一个整数的倒序，没啥说的，在long类型上比较来避免overflow。  AC代码： 1 class Solution { 2 pub
·2015-11-02 17:37

LeetCode题解(8)--String to Integer (atoi)

Implement atoi to convert a string to an integer. Hint: Carefully consider all possible input cases. If you want a challenge, please do not see below and ask yourself what are the poss
·2015-11-02 17:37

LeetCode题解(6)--ZigZag Conversion

  The string "PAYPALISHIRING" is written in a zigzag pattern on a given number of rows like this: (you may want to display this pattern in a fixed font for better legibility)
·2015-11-02 17:36

LeetCode题解(3)-- Longest Substring Without Repeating Characters

Given a string, find the length of the longest substring without repeating characters. For example, the longest substring without repeating letters for "abcabcbb" is "abc", which t
·2015-11-02 17:35

LeetCode题解(2)-- Add Two Numbers

原题：  　　　　　　　　https://leetcode.com/problems/add-two-numbers/ You are given two linked lists representing two non-negative numbers. The digits are stored in reverse order and each of their nodes c
·2015-11-02 17:35

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
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