Category Git
Short answers to the question what is the difference between...
Short answers to the question how to revert a git...
Short answers to the question how to modify existing unpushed...
Short answers to the question how to undo a git...
Short answers to the question how to rename a local...
Short answers to the question how to delete a git...
Short answers to the question how to checkout a remote...
Short answers to the question how to undo the most...
Category MySQL
How to make multiple columns unique (together) in an existing...
Suppose we have the following REIMBURSEMENT table, find the max...
How to get the size of a table in MySQL...
How to get the size of a database in MySQL...
How to concatenate multiple rows into one field in MySQL...
Given a table EMPLOYEE, change the data type of the...
How to set a default value for a MySQL Datetime...
This query writes results into a CSV file on the...
MySQL stores the user information in its own database.
Do a SELECT with a GROUP BY clause.
The INNER JOIN keyword selects records that have matching values...
Aliases are nicknames. They give us a shorthand way of...
The OR operator combines two Boolean expressions and returns true...
The LIMIT clause is used in the SELECT statement to...
The LIKE operator is used in a WHERE clause to...
To test whether a value is NULL or not, we...
The IN operator allows us to determine if a specified...
The BETWEEN operator selects values within a given range.
The AND operator is a logical operator that combines two...
The WHERE clause allows us to choose which rows are...
In order to remove duplicate rows, we use the DISTINCT...
The ORDER BY clause is used to sort the result-set...
The SELECT statement allows us to read data from one...
Category Database
LeetCode 1939. Write an SQL query to find the IDs...
LeetCode 1949. Write an SQL query to find all the...
LeetCode 1919. Write an SQL query to report the similar...
LeetCode 1917. Write an SQL query to recommend friends to...
LeetCode 1972. Write an SQL query to report the IDs...
LeetCode 1988. Write an SQL query to report the minimum...
LeetCode 1965. Write an SQL query to report the IDs...
LeetCode 1978. Write an SQL query to report the IDs...
LeetCode 1990. Write an SQL query to report the number...
LeetCode 1907. Write an SQL query to report the number...
LeetCode 1934. Write an SQL query to find the confirmation...
LeetCode 1951. Write an SQL query to find all the...
LeetCode 1890. Write an SQL query to report the latest...
LeetCode 1843. Write an SQL query to report the IDs...
LeetCode 1892. Write an SQL query to find all the...
LeetCode 1867. Write an SQL query to find the order_id...
LeetCode 1831. Write an SQL query to report the IDs...
LeetCode 1841. Write an SQL query to report the statistics...
LeetCode 1875. Write an SQL query to report the IDs...
LeetCode 1821. Write an SQL query to report the customers...
LeetCode 1853. Write an SQL query to convert each date...
LeetCode 1873. Write an SQL query to calculate the bonus...
LeetCode 1795. Write an SQL query to rearrange the Products...
LeetCode 1811. Write an SQL query to report the name...
LeetCode 1809. Write an SQL query to report all the...
LeetCode 1789. Write an SQL query to report all the...
LeetCode 1783. Write an SQL query to report the number...
LeetCode 1777. Write an SQL query to find the price...
LeetCode 1767. Write an SQL query to report the IDs...
LeetCode 1757. Write an SQL query to find the ids...
LeetCode 1747. Write an SQL query to find the account_id...
LeetCode 1741. Write an SQL query to calculate the total...
LeetCode 1731. Write an SQL query to report the ids...
LeetCode 1729. Write an SQL query that will, for each...
LeetCode 1715. Write an SQL query to count the number...
LeetCode 1709. Write an SQL query that will, for each...
LeetCode 1384. Write an SQL query to report the Total...
LeetCode 1479. Write an SQL query to report how many...
LeetCode 1651. Write an SQL query to compute the average_ride_distance...
LeetCode 1369. Write an SQL query to show the second...
LeetCode 1412. Write an SQL query to report the students...
LeetCode 1194. Write an SQL query to find the winner...
LeetCode 618. A U.S graduate school has students from Asia,...
LeetCode 1225. Write an SQL query to generate a report...
LeetCode 569. Write a SQL query to find the median...
LeetCode 1159. Write an SQL query to find for each...
LeetCode 1635. Write an SQL query to report the following...
LeetCode 1097. Write an SQL query that reports for each...
LeetCode 1127. Write an SQL query to find the total...
LeetCode 262. Write a SQL query to find the cancellation...
LeetCode 1336. Write an SQL query to find how many...
LeetCode 601. Write an SQL query to display the records...
LeetCode 1645. Write an SQL query to report the percentage...
LeetCode 571. Write a query to find the median of...
LeetCode 579. Write a SQL to get the cumulative sum...
LeetCode 185. Write a SQL query to find employees who...
LeetCode 615. Given two tables as below, write a query...
LeetCode 1098. Write an SQL query that reports the books...
LeetCode 614. Please write a sql query to get the...
LeetCode 1132. Write an SQL query to find the average...
LeetCode 1699. Write an SQL query to report the number...
LeetCode 177. Write a SQL query to get the nth...
LeetCode 1107. Write an SQL query that reports for every...
LeetCode 1205. Write an SQL query to find for each...
LeetCode 578. Write a sql query to identify the question...
LeetCode 184. Write a SQL query to find employees who...
LeetCode 1149. Write an SQL query to find all the...
LeetCode 1454. Write an SQL query to find the id...
LeetCode 574. Write a sql to find the name of...
LeetCode 1212. Write an SQL query that selects the team_id,...
LeetCode 178. Write a SQL query to rank scores. If...
LeetCode 1070. Write an SQL query that selects the product...
LeetCode 1341. Write the following SQL query to find the...
LeetCode 585. Write a query to print the sum of...
LeetCode 1174. Write an SQL query to find the percentage...
LeetCode 602. In social network like Facebook or Twitter, people...
LeetCode 1501. Write an SQL query to find the countries...
LeetCode 580. A university uses 2 data tables, student and...
LeetCode 1555. Our bank records all transactions in the table...
LeetCode 608. Given a table tree, id is identifier of...
LeetCode 1549. Write an SQL query to find the most...
LeetCode 612. Write a query to find the shortest distance...
LeetCode 1459. Write an SQL query to report of all...
LeetCode 1164. Write an SQL query to find the prices...
LeetCode 1264. Write an SQL query to recommend pages to...
LeetCode 1193. Write an SQL query to find for each...
LeetCode 1158. Write an SQL query to find for each...
LeetCode 570. Given the Employee table, write a SQL query...
LeetCode 1613. Write an SQL query to find the missing...
LeetCode 626. Mary is a teacher in a middle school...
LeetCode 1045. Write an SQL query for a report that...
LeetCode 1126. Write an SQL query to find all active...
LeetCode 1532. Write an SQL query to find the most...
LeetCode 1321. You are the restaurant owner and you want...
LeetCode 1077. Write an SQL query that reports the most...
LeetCode 1364. Write an SQL query to find the following...
LeetCode 1421. Write an SQL query to find the npv...
LeetCode 1204. Write an SQL query to find the person_name...
LeetCode 1112. Write a SQL query to find the highest...
LeetCode 1440. Write an SQL query to evaluate the boolean...
LeetCode 1468. Write an SQL query to find the salaries...
LeetCode 1355. Write an SQL query to find the names...
LeetCode 1142. Write an SQL query to find the average...
LeetCode 1596. Write an SQL query to find the most...
LeetCode 1308. Write an SQL query to find the total...
LeetCode 1495. Write an SQL query to report the distinct...
LeetCode 597. Write an SQL query to find the overall...
LeetCode 1285. Write an SQL query to find the start...
LeetCode 1398. Write an SQL query to report the customer_id...
LeetCode 596. Please list out all classes which have more...
LeetCode 1393. Write an SQL query to report the Capital...
LeetCode 619. Table my_numbers contains many numbers in column num...
LeetCode 1445. Write an SQL query to report the difference...
LeetCode 1270. Write an SQL query to find employee_id of...
LeetCode 1294. Write an SQL query to find the type...
LeetCode 1141. Write an SQL query to find the daily...
LeetCode 610. A pupil Tim gets homework to identify whether...
LeetCode 1280. Write an SQL query to find the number...
LeetCode 607. Given three tables, salesperson, company, orders.
LeetCode 1084. Write an SQL query that reports the products...
LeetCode 1083. Write an SQL query that reports the buyers...
LeetCode 1113. Write an SQL query that reports the number...
LeetCode 1211. Write an SQL query to find each query_name,...
LeetCode 1076. Write an SQL query that reports all the...
LeetCode 1075. Write an SQL query that reports the average...
LeetCode 1241. Write an SQL query to find number of...
LeetCode 620. X city opened a new cinema, many people...
LeetCode 1543. Write an SQL query to report product_name in...
LeetCode 603. Several friends at a cinema ticket office would...
LeetCode 1322. A company is running Ads and wants to...
LeetCode 1407. Write an SQL query to report the distance...
LeetCode 627. Given a table salary, such as the one...
LeetCode 613. Write a query to find the shortest distance...
LeetCode 1082. Write an SQL query that reports the best...
LeetCode 1179. Write an SQL query to reformat the table...
LeetCode 1069. Write an SQL query that reports the total...
LeetCode 1068. Write an SQL query that reports all product...
LeetCode 1327. Write an SQL query to get the names...
LeetCode 1173. Write an SQL query to find the percentage...
LeetCode 1517. Write an SQL query to find the users...
LeetCode 584. Given a table customer holding customers information and...
LeetCode 586. Query the customer_number from the orders table for...
LeetCode 1511. Write an SQL query to report the customer_id...
LeetCode 1435. You want to know how long a user...
LeetCode 595. Write a SQL solution to output big countries’...
LeetCode 1251. Write an SQL query to find the average...
LeetCode 1148. Write an SQL query to find all the...
LeetCode 1050. Write a SQL query for a report that...
LeetCode 1565. Write an SQL query to find the number...
LeetCode 1607. Write an SQL query to report the names...
LeetCode 197. Write an SQL query to find all dates’...
LeetCode 550. Write an SQL query that reports the fraction...
LeetCode 534. Write an SQL query that reports for each...
LeetCode 512. Write a SQL query that reports the device...
LeetCode 511. Write an SQL query that reports the first...
LeetCode 577. Select all employee’s name and bonus whose bonus...
LeetCode 196. Write a SQL query to delete all duplicate...
LeetCode 1693. Write an SQL query that will, for each...
LeetCode 1581. Write an SQL query to find the IDs...
LeetCode 1677. Write an SQL query that will, for all...
LeetCode 1633. Write an SQL query to find the percentage...
LeetCode 1667. Write an SQL query to fix the names...
LeetCode 182. Write a SQL query to find all duplicate...
LeetCode 183. Write a SQL query to find all customers...
LeetCode 180. Write an SQL query to find all numbers...
LeetCode 1661. There is a factory website that has several...
LeetCode 176. Given the Employee table, write a SQL query...
LeetCode 181. Given the Employee table, write a SQL query...
LeetCode 1587. Write an SQL query to report the name...
LeetCode 1484. Write an SQL query to find for each...
LeetCode 1623. Write an SQL query to find all the...
LeetCode 1571. Write an SQL query to report how much...
LeetCode 1350. Write an SQL query to find the id...
LeetCode 1378. Write an SQL query to show the unique...
LeetCode 1527. Write an SQL query to report the patient_id,...
LeetCode 1683. Write an SQL query to find the IDs...
LeetCode 1303. Write an SQL query to find the team...
LeetCode 175. Write a SQL query for a report that...
Category List
A growing list of Git questions and short answers.
A growing list of MySQL tutorials.
A list of LeetCode database problems and solutions.
A growing list of LeetCode problems and solutions.
A growing list of posts under the topic of Operating...
A growing list of posts under the topic of Object...
A growing list of posts under the topic of C++...
Category Operating System
Another important question is how threads interact when they access...
A thread is an abstraction for a single running process....
How can the OS provide the illusion of nearly-endless supply...
How can the OS decide which page(s) to evict from...
How can the OS make use of a larger, slower...
How can we make page tables smaller.
How can we speed up address translation, and generally avoid...
How can we virtualize memory with pages, so as to...
How to support a large address space with (potentially) a...
How can we relocate the process in memory in a...
Virtual Memory is an abstraction that the Operating System provides...
Category Object-Oriented Design
Design the data structures for an online book reader system...
Design a parking lot using object-oriented principles. We will focus...
An object oriented design problem. Imagine you have a call...
Category Design Pattern
The singleton design pattern is a type of creational pattern...
The factory design pattern is a type of creational pattern...
Category C++ Concepts
Every C++ expression has a type and belongs to a...
Perfect forwarding reduces the need for overloaded functions and helps...
The rvalue references enable us to distinguish an lvalue from...
A reference is an alias of another object. It stores...
An lvalue reference is another name of an object. An...
A lambda expression is a convenient way of defining an...
A template specialization is a separate definition in which the...
C++ transforms the operands to a common type before performing...
An explicit conversion is also called as a cast. There...
The constructor that takes a single parameter that is a...
A function specified as inline is expanded everywhere it is...
A function pointer is a pointer that denotes a function...
Sometimes an object must store a way to access the...
A friend class can access private and protected members of...
A unique_ptr does not share its pointer. It cannot be...
In modern C++ programming, the Standard Library includes smart pointers,...
The shared_ptr type is a smart pointer that is designed...
A template is a blueprint or formula for creating a...
Polymorphism means having more than one function with the same...
An interface describes the behavior or capabilities of a C++...
Category Data Structure
LeetCode 914. In a deck of cards, each card has...
LeetCode 916. You are given two string arrays words1 and...
LeetCode 874. A robot on an infinite XY-plane starts at...
LeetCode 987. Given the root of a binary tree, calculate...
LeetCode 946. Given two integer arrays pushed and popped each...
LeetCode 903. You are given a string s of length...
LeetCode 941. Given an array of integers arr, return true...
LeetCode 965. A binary tree is uni-valued if every node...
LeetCode 980. You are given an m x n integer...
LeetCode 804. International Morse Code defines a standard encoding where...
LeetCode 929. Every valid email consists of a local name...
LeetCode 884. A sentence is a string of single-space separated...
LeetCode 982. Given an integer array nums, return the number...
LeetCode 867. Given a 2D integer array matrix, return the...
LeetCode 981. Design a time-based key-value data structure that can...
LeetCode 927. You are given an array arr which consists...
LeetCode 956. You are installing a billboard and want it...
LeetCode 892. You are given an n x n grid...
LeetCode 887. You are given k identical eggs and you...
LeetCode 891. The width of a sequence is the difference...
LeetCode 907. Given an array of integers arr, find the...
LeetCode 985. You are given an integer array nums and...
LeetCode 834. There is an undirected connected tree with n...
LeetCode 811. A website domain “discuss.leetcode.com” consists of various subdomains....
LeetCode 992. Given an integer array nums and an integer...
LeetCode 984. Given two integers a and b, return any...
LeetCode 877. Alice and Bob play a game with piles...
LeetCode 936. You are given two strings stamp and target....
LeetCode 977. Given an integer array nums sorted in non-decreasing...
LeetCode 805. You are given an integer array nums.
LeetCode 842. You are given a string of digits num,...
LeetCode 808. There are two types of soup, type A...
LeetCode 905. Given an integer array nums, move all the...
LeetCode 922. Given an array of integers nums, half of...
LeetCode 912. Given an array of integers nums, sort the...
LeetCode 909. You are given an n x n integer...
LeetCode 865. Given the root of a binary tree, the...
LeetCode 988. You are given the root of a binary...
LeetCode 908. You are given an integer array nums and...
LeetCode 839. Two strings Xand Yare similar if we can...
LeetCode 862. Given an integer array nums and an integer...
LeetCode 847. You have an undirected, connected graph of n...
LeetCode 864. You are given an m x n grid...
LeetCode 821. Given a string s and a character c...
LeetCode 934. You are given an n x n binary...
LeetCode 820. A valid encoding of an array of words...
LeetCode 848. You are given a string s of lowercase...
LeetCode 856. Given a balanced parentheses string s, return the...
LeetCode 861. You are given an m x n binary...
LeetCode 990. You are given an array of strings equations...
LeetCode 994. You are given an m x n grid...
LeetCode 900. We can use run-length encoding (i.e., RLE) to...
LeetCode 917. Given a string s, reverse the string according...
LeetCode 950. You are given an integer array deck. There...
LeetCode 869. You are given an integer n. We reorder...
LeetCode 937. You are given an array of logs. Each...
LeetCode 959. An n x n grid is composed of...
LeetCode 836. An axis-aligned rectangle is represented as a list...
LeetCode 882. You are given an undirected graph (the “original...
LeetCode 938. Given the root node of a binary search...
LeetCode 818. Your car starts at position 0 and speed...
LeetCode 883. You are given an n x n grid...
LeetCode 879. There is a group of n members, and...
LeetCode 957. There are 8 prison cells in a row...
LeetCode 866. Given an integer n, return the smallest prime...
LeetCode 970. Given three integers x, y, and bound, return...
LeetCode 886. We want to split a group of n...
LeetCode 830. In a string sof lowercase letters, these letters...
LeetCode 852. Let’s call an array arr a mountainif the...
LeetCode 915. Given an integer array nums, partition it into...
LeetCode 969. Given an array of integers arr, sort the...
LeetCode 899. You are given a string s and an...
LeetCode 901. Design an algorithm that collects daily price quotes...
LeetCode 911. You are given two integer arrays persons and...
LeetCode 975. You are given an integer array arr. From...
LeetCode 967. Return all non-negative integers of length n such...
LeetCode 902. Given an array of digits which is sorted...
LeetCode 933. You have a RecentCounter class which counts the...
LeetCode 920. Your music player contains n different songs. You...
LeetCode 806. You are given a string s of lowercase...
LeetCode 878. A positive integer is magical if it is...
LeetCode 837. Alice plays the following game, loosely based on...
LeetCode 947. On a 2D plane, we place n stones...
LeetCode 826. You have n jobs and m workers. You...
LeetCode 819. Given a string paragraph and a string array...
LeetCode 896. An array is monotonic if it is either...
LeetCode 858. There is a special square room with mirrors...
LeetCode 801. You are given two integer arrays of the...
LeetCode 995. You are given a binary array nums and...
LeetCode 945. You are given an integer array nums. In...
LeetCode 931. Given an n x n array of integers...
LeetCode 1000. There are n piles of stones arranged in...
LeetCode 857. There are n workers. You are given two...
LeetCode 983. You have planned some train traveling one year...
LeetCode 939. You are given an array of points in...
LeetCode 921. A parentheses string is valid if and only...
LeetCode 924. You are given a network of n nodes...
LeetCode 928. You are given a network of n nodes...
LeetCode 876. Given the head of a singly linked list,...
LeetCode 962. A ramp in an integer array nums is...
LeetCode 918. Given a circular integer array nums of length...
LeetCode 895. Design a stack-like data structure to push elements...
LeetCode 998. A maximum tree is a tree where every...
LeetCode 849. You are given an array representing a row...
LeetCode 807. There is a city composed of n x...
LeetCode 831. You are given a personal information string s,...
LeetCode 827. You are given an n x n binary...
LeetCode 840. A 3 x 3 magic square is a...
LeetCode 851. There is a group of n people labeled...
LeetCode 978. Given an integer array arr, return the length...
LeetCode 845. Given an integer array arr, return the length...
LeetCode 925. Your friend is typing his name into a...
LeetCode 817. You are given the head of a linked...
LeetCode 873. Given a strictly increasing array arr of positive...
LeetCode 964. Given a single positive integer x, we will...
LeetCode 872. Consider all the leaves of a binary tree,...
LeetCode 812. Given an array of points on the X-Y...
LeetCode 949. Given an arrayarr of 4 digits, find the...
LeetCode 813. You are given an integer array nums and...
LeetCode 976. Given an integer array nums, return the largest...
LeetCode 854. Strings s1 and s2 are k-similar (for some...
LeetCode 973. Given an array of points where points[i] =...
LeetCode 897. Given the root of a binary search tree,...
LeetCode 846. Alice has some number of cards and she...
LeetCode 893. You are given an array of strings of...
LeetCode 904. You are visiting a farm that has a...
LeetCode 926. A binary string is monotone increasing if it...
LeetCode 951. For a binary tree T, we can define...
LeetCode 971. You are given the root of a binary...
LeetCode 943. Given an array of strings words, return the...
LeetCode 890. Given a list of strings words and a...
LeetCode 972. Given two strings s and t, each of...
LeetCode 944. You are given an array of n strings...
LeetCode 960. You are given an array of n strings...
LeetCode 955. You are given an array of n strings...
LeetCode 880. You are given an encoded string s. To...
LeetCode 993. Given the root of a binary tree with...
LeetCode 828. Let’s define a function countUniqueChars(s) that returns the...
LeetCode 889. Given two integer arrays, preorder and postorder where...
LeetCode 829. Given an integer n, return the number of...
LeetCode 919. A complete binary tree is a binary tree...
LeetCode 958. Given the root of a binary tree, determine...
LeetCode 810. You are given an array of integers nums...
LeetCode 913. A game on an undirected graph is played...
LeetCode 822. You are given n cards, with a positive...
LeetCode 853. There are n cars going to the same...
LeetCode 815. You are given an array routes representing bus...
LeetCode 859. Given two strings s and goal, return true...
LeetCode 991. There is a broken calculator that has the...
LeetCode 803. You are given an m x n binary...
LeetCode 881. You are given an array people where people[i]...
LeetCode 898. We have an array arr of non-negative integers....
LeetCode 823. Given an array of unique integers, arr, where...
LeetCode 814. Given the root of a binary tree, return...
LeetCode 968. You are given the root of a binary...
LeetCode 930. Given a binary array nums and an integer...
LeetCode 868. Given a positive integer n, find and return...
LeetCode 932. Given the integer n, return any beautiful array...
LeetCode 948. You have an initial power of power, an...
LeetCode 844. Given two strings s and t, return true...
LeetCode 999. On an 8 x 8 chessboard, there is...
LeetCode 954. Given an integer array of even length arr,...
LeetCode 816. We had some 2-dimensional coordinates, like “(1, 3)”...
LeetCode 894. Given an integer n, return a list of...
LeetCode 863. Given the root of a binary tree, the...
LeetCode 870. You are given two integer arrays nums1 and...
LeetCode 989. The array-form of an integer num is an...
LeetCode 923. Given an integer array arr, and an integer...
LeetCode 611. Given an integer array nums, return the number...
LeetCode 794. Given a Tic-Tac-Toe board as a string array...
LeetCode 678. Given a string s containing only three types...
LeetCode 680. Given a string s, return true if the...
LeetCode 782. You are given an n x n binary...
LeetCode 692. Given an array of strings words and an...
LeetCode 766. Given an m x n matrix, returntrueif the...
LeetCode 621. Given a characters array tasks, representing the tasks...
LeetCode 778. You are given an n x n integer...
LeetCode 777. In a string composed of ‘L’, ‘R’, and...
LeetCode 664. There is a strange printer with the following...
LeetCode 691. We are given n different types of stickers....
LeetCode 725. Given the head of a singly linked list...
LeetCode 761. Special binary strings are binary strings with the...
LeetCode 640. Solve a given equation and return the value...
LeetCode 773. On an 2 x 3 board, there are...
LeetCode 638. In LeetCode Store, there are n items to...
LeetCode 645. You have a set of integers s, which...
LeetCode 757. You are given a 2D integer array intervals...
LeetCode 728. A self-dividing number is a number that is...
LeetCode 657. There is a robot starting at the position...
LeetCode 767. Given a string s, rearrange the characters of...
LeetCode 684. In this problem, a tree is an undirected...
LeetCode 685. In this problem, a rooted tree is a...
LeetCode 780. Given four integers sx, sy, tx, and ty,...
LeetCode 715. A Range Module is a module that tracks...
LeetCode 710. You are given an integer n and an...
LeetCode 781. There is a forest with an unknown number...
LeetCode 756. You are stacking blocks to form a pyramid....
LeetCode 793. Let f(x) be the number of zeroes at...
LeetCode 763. You are given a string s. We want...
LeetCode 736. You are given a string expression representing a...
LeetCode 752. You have a lock in front of you...
LeetCode 743. You are given a network of n nodes,...
LeetCode 732. A k-booking happens when k events have some...
LeetCode 731. You are implementing a program to use as...
LeetCode 729. You are implementing a program to use as...
LeetCode 688. On an n x n chessboard, a knight...
LeetCode 779. We build a table of n rows (1-indexed)....
LeetCode 724. Given an array of integers nums, calculate the...
LeetCode 636. On a single-threaded CPU, we execute a program...
LeetCode 789. You are playing a simplified PAC-MAN game on...
LeetCode 649. In the world of Dota2, there are two...
LeetCode 741. You are given an n x n grid...
LeetCode 650. There is only one character ‘A’ on the...
LeetCode 653. Given the root of a Binary Search Tree...
LeetCode 669. Given the root of a binary search tree...
LeetCode 709. Given a string s, return the string after...
LeetCode 633. Given a non-negative integer c, decide whether there’re...
LeetCode 659. You are given an integer array nums that...
LeetCode 798. You are given an array nums. You can...
LeetCode 632. You have k lists of sorted integers in...
LeetCode 748. Given a string licensePlate and an array of...
LeetCode 671. Given a non-empty special binary tree consisting of...
LeetCode 700. You are given the root of a binary...
LeetCode 788. An integer x is a good if after...
LeetCode 796. Given two strings s and goal, return true...
LeetCode 686. Given two string s a and b, return...
LeetCode 722. Given a C++ program, remove comments from it....
LeetCode 754. You are standing at position 0 on an...
LeetCode 655. Given the root of a binary tree, construct...
LeetCode 762. Given two integers left and right, return the...
LeetCode 745. Design a special dictionary with some words that...
LeetCode 698. Given an integer array nums and an integer...
LeetCode 795. Given an integer array nums and two integers...
LeetCode 792. Given a string s and an array of...
LeetCode 673. Given an integer arraynums, return the number of...
LeetCode 726. Given a string formula representing a chemical formula,return...
LeetCode 665. Given an array nums with n integers, your...
LeetCode 738. An integer has monotone increasing digits if and...
LeetCode 783. Given the root of a Binary Search Tree...
LeetCode 712. Given two strings s1 ands2, return the lowest...
LeetCode 746. You are given an integer array cost where...
LeetCode 617. You are given two binary trees root1 and...
LeetCode 662. Given the root of a binary tree, return...
LeetCode 689. Given an integer array nums and an integer...
LeetCode 628. Given an integer array nums, find three numbers...
LeetCode 718. Given two integer arrays nums1 and nums2, return...
LeetCode 646. You are given an array of n pairs...
LeetCode 769. You are given an integer array arr of...
LeetCode 768. You are given an integer array arr.
LeetCode 687. Given the root of a binary tree, return...
LeetCode 674. Given an unsorted array of integers nums, return...
LeetCode 784. Given a string s, we can transform every...
LeetCode 668. Nearly everyone has used the Multiplication Table. The...
LeetCode 785. There is an undirected graph with n nodes,...
LeetCode 661. An image smoother is a filter of the...
LeetCode 775. You are given an integer array nums of...
LeetCode 733. An image is represented by an m x...
LeetCode 744. Given a characters array letters that is sorted...
LeetCode 609. Given a list paths of directory info, including...
LeetCode 699. There are several squares being dropped onto the...
LeetCode 622. Design your implementation of the circular queue. The...
LeetCode 641. Design your implementation of the circular double-ended queue...
LeetCode 675. You are asked to cut off all the...
LeetCode 647. Given a string s, return the number of...
LeetCode 670. You are given an integer num. You can...
LeetCode 654. You are given an integer array nums with...
LeetCode 643. You are given an integer array nums consisting...
LeetCode 695. You are given an m x n binary...
LeetCode 677. Design a map that allows you to do...
LeetCode 764. You are given an integer n. You have...
LeetCode 747. You are given an integer array nums where...
LeetCode 703. Design a class to find the k^th largest...
LeetCode 786. You are given a sorted integer array arr...
LeetCode 629. For an integer array nums, an inverse pair...
LeetCode 701. You are given the root node of a...
LeetCode 676. Design a data structure that is initialized with...
LeetCode 719. The distance of a pair of integers a...
LeetCode 658. Given a sorted integer array arr, two integers...
LeetCode 652. Given the rootof a binary tree, return all...
LeetCode 690. You have a data structure of employee information,...
LeetCode 790. You have two types of tiles, a 2...
LeetCode 707. Design your implementation of the linked list. You...
LeetCode 705. Design a HashSet without using any built-in hash...
LeetCode 706. Design a HashMap without using any built-in hash...
LeetCode 740. You are given an integer array nums. You...
LeetCode 697. Given a non-empty array of non-negative integers nums,...
LeetCode 639. A message containing letters from A-Z can be...
LeetCode 739. Given an array of integers temperatures represents the...