hackerrank vs leetcode

Given a binary tree, determine if it is a valid binary search tree (BST).Assume a BST is defined as follows: The left subtree of a node contains only nodes with keys less than the node ' s key. The right subtree of a node contains only nodes with keys greater than the node ' s key. Both the left and right subtrees must also is binary search trees. Leetcode has given the definition of a two-fork search tree.classSolution:#@param r

See today Cool Shell recommended foreign Programming leetcode Algorithmic Programming web site , there are currently 154 algorithms, the feeling is very interesting, ordinary work is also relatively busy, now very little time to exercise algorithm related things, there is a time to calm down the heart, review the foundation, active under the idea of self, is also necessary. in the afternoon, I did a simple question, and then we added some other questi

I. Description of the topicGiven a singly linked list l: l0→l1→ ... →ln-1→lN,Reorder it to: l0→ln→l1→ln-1→l2→L n-2→ ...You must does this in-place without altering the nodes ' values.For example,Given {1,2,3,4} , reorder it to {1,4,2,3} .Second, analysis1. Violence solutionThe time required for this solution is relatively high in complexity, O (N2)　　The code is as follows: the code submitted on Leetcode will prompt for timeouts Public voidreorderlist

Preface I did not expect that the junior still heavy schoolwork, coupled with some trivial, and their own inertia, many plans are not enough heart, but do not want to go on like this, recently reviewed his skills in the learning algorithm tree points, found that some of the basic algorithms and classical algorithms are really so little swallowed, So there is a brush Leetcode plan, one is to Restudying, the second is to familiarize yourself with Java

"Leetcode" single Number Problem solving report (Java Python) [Leetcode] Https://leetcode.com/problems/single-number/Total accepted:183838 Total submissions:348610 difficulty:easy Question Given an array of integers, every element appears twice for one. Find is single one.Note:Your algorithm should have a linear runtime. Could you implement it without using extra memory? Ways I was too weak, the problem

"title" Topic linkGiven a 2D binary matrix filled with 0 "s and 1 ' s, find the largest rectangle containing only 1 's and return their area. For example, given the following matrix: 1 0 1 0 01 0 1 1 11 1 1 1 11 0 0 1 0 Return 6 "Analysis" RuntimeAt first I think it can be a dynamic planning idea, such as: MATRIX[I-1][J-1]–>MATRIX[I][J] orMATRIX[I-1][J-1],MATRIX[I-1][J],MATRIX[I][J-1]–>MATRIX[I][J] After several thoughts and practice, it seems that it is not going through(Note: But this kind of

[Leetcode/javascript] 461.Hamming Distance Topic The Hamming distance between two integers is the number of positions at which the corresponding bits are different. Given two integers x and y, calculate the Hamming distance. Note:0≤x, y Example: input:x = 1, y = 4 Output:2 Explanation:1 (0 0 0 1)4 (0 1 0 0)? ? The above arrows point to positions where the corresponding bits are different. Analysis The topic is very simple, given two 32-bit integers

"Leetcode" Find all Numbers disappeared the problem-solving report in an Array [Leetcode] Https://leetcode.com/problems/find-all-numbers-disappeared-in-an-array/Total accepted:14302 Total Submissions: 24993 difficulty:easy Question Given an array of integers where 1≤a[i]≤n (n = size of array),Some elements appear twice and others appear. Find all the elements of [1, N] inclusive which does not appear in th

Tags: Leetcode sqlThe Employee table holds all employees including their managers. Every employee has an ID, and there is also a column for the manager ID.+----+-------+--------+-----------+| Id | Name | Salary | ManagerID |+----+-------+--------+-----------+| 1 | Joe | 70000 | 3 || 2 | Henry | 80000 | 4 || 3 | Sam | 60000 | NULL || 4 | Max | 90000 | NULL |+----+-------+--------+-----------+Given The Employee table, write a SQL query, finds out employ

Today, we begin to regularly record the interesting topics that people encounter when they brush their leetcode.517 Super Washing machines you has n Super washing machines on a line. Initially, each washing machine have some dresses or is empty.For each move, you could choose any m (1≤m≤n) washing machines, and pass one dress of each washing TS adjacent washing machines at the same time.Given an integer array representing the number of dresses in each

Label:On the way to the lab with John Chen in the morning, listen to him. Leetcode also has a database and shell practice. So take to practice practiced hand, found the database of the problem only a few and do also quickly AC rate is quite high, right when review the basic grammar of the database. 1:employees earning more Than their Managers The Employee table holds all employees including their managers. Every employee has an ID, and there is also

Leetcode Original Quote:Write a SQL query to delete all duplicate e-mail entries in a table named Person , keeping unique emails based on its smallest Id. +----+------------------+| Id | Email |+----+------------------+| 1 | [Emailprotected] | | 2 | [Emailprotected] | | 3 | [emailprotected] |+----+------------------+id is the primary key, column for this table. For example, after running your query, the above Person table

(2015/11/3)LeetCode-36 Valid Sudoku: (Easy)1) Using Data structuresSetVector2) Subscript 0-8 stores the number in the row, 9-17 stores the number in the column, and 18-26 stores the number in the 3x3 block.3) Double for loop, I means row, 9 + j for column, + I/3 + 3 * (J/3) for block.(2015/11/12)LeetCode-38 Count and Say: (Easy)1) determine the parameter n, return the part of the direct output.2) dual for l

Python bit operation:Bitwise AND , Bitwise OR |Don't realizeBitwise XOR or ^num ^ num = 0Shift left num Shift Right >>num >> 2 = = Num/2**2Take counter ~~num = =-(num + 1)1. Single numberGiven an array of integers, every element appears twice except for One. Find the single One.Note:Your algorithm should has a linear runtime Complexity. Could you implement it without using extra memory?The key point is that the same integer bitwise XOR is 0, the integer and 0 are different or unchanged, and a re

Dynamic programming is a very important algorithm design idea. Historically there have been many well-known algorithms based on this idea, such as: Needleman–wunsch algorithm, CYK algorithm, FFT algorithm, Viterbi algorithm and so on. There are two core ideas in dynamic programming: First, to disassemble a large problem into several sub problems, and then to store the results that have been calculated for multiple use. Dynamic planning is important because it is a frequent focus of written inte

Problem A two non-empty list is given to represent two non-negative integers. The digits are stored in reverse order, with each node storing only a single number. Adds two numbers to return a new linked list.You can assume that except for the number 0, none of the two numbers will start with 0.Example: Input: (2, 4, 3) + (5, 6, 4) output: 7, 0, 8 reason: 342 + 465 = 807 Code implementation#include 　　Recommended"Leetcode" algorithm 22 nu

ifHead = = None:returnHead Dummy=listnode (0) Dummy.next=Head Start= Dummy#start =0. Given this linked list:1->2->3->4->5 # for k = 2, you should return:2->1->4->3->5 whileStart.next:end= Start#end = 0 forIinchRange (k-1): End= End.next#end = 1 ifEnd.next = = None:returnDummy.next (Start.next, start)=self.reverse (Start.next, End.next)#(start.next=3, Start=1) =self.reverse (start.next=1, end.next=2) returnDummy.nextdefreverse (self, start, end):

(inti=asize-1;i>=0;i--) { AResult.add (Addnumber +Result.get (i)); at } - returnresult; - } -}Then I saw the simpler way. Gray code, binary transcoding method is the binary pre-complement 0, and then two-bit XOR. GI = bi ^ bi+1 such as binary 0101, before adding 0 after 00101,Then the right-to-left 22-bit XOR 0111 (the difference is 1, the same as 0), get Gray code 0111, in fact, is the binary x Do (x>>1) ^x operation.1 Public classSolution {

Given an integer, convert it to a Roman numeral.Input is guaranteed to being within the range from 1 to 3999.Build two list match Roman numerals in turn. Some of the more special ones are Roman numerals with two digits.From http://www.cnblogs.com/zuoyuan/p/3779581.htmlThis practice is to see the best understand, so it is used.Class solution: # @return A string def inttoroman (self, num): values=[ 1000,900,500,400,100,90,50,40,10,9,5,4,1] roman=[' M ', ' CM ', ' D ', ' CD ', '

easy!Title Description:Converts an ordered array in ascending order to a highly balanced binary search tree.In the subject, a highly balanced binary tree refers to the absolute value of the height difference of the left and right two subtrees of each node of a binary tree not exceeding 1.Example:Given an ordered array: [ -10,-3,0,5,9], one possible answer is: [0,-3,9,-10,null,5], which can represent the following highly balanced binary search tree: 0 / -3 9 / /-10 5Problem Sol