01 2018 档案
摘要：A matrix is Toeplitz if every diagonal from top-left to bottom-right has the same element. Now given an M x N matrix, return True if and only if the m
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摘要：内连接(INNER JOIN)： 分为三种 等值连接、自然连接、不等连接 外连接(OUTER JOIN)： 左外连接(LEFT OUTER JOIN或LEFT JOIN) 右外连接(RIGHT OUTER JOIN或RIGHT JOIN) 全外连接(FULL OUTER JOIN或FULL JOIN
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摘要：Given an array of integers, 1 ≤ a[i] ≤ n (n = size of array), some elements appear twice and others appear once. Find all the elements that appear twi
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摘要：Write a SQL query to delete all duplicate email entries in a table named Person, keeping only unique emails based on its smallest Id. For example, aft
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摘要：Given a Weather table, write a SQL query to find all dates' Ids with higher temperature compared to its previous (yesterday's) dates. For example, ret
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摘要：Given a table salary, such as the one below, that has m=male and f=female values. Swap all f and m values (i.e., change all f values to m and vice ver
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摘要：Write a SQL query to get the second highest salary from the Employee table. For example, given the above Employee table, the query should return 200 a
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摘要：There is a table courses with columns: student and class Please list out all classes which have more than or equal to 5 students. For example, the tab
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摘要：Suppose that a website contains two tables, the Customers table and the Orders table. Write a SQL query to find all customers who never order anything
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摘要：The Employee table holds all employees including their managers. Every employee has an Id, and there is also a column for the manager Id. Given the Em
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摘要：Write a SQL query to find all duplicate emails in a table named Person. For example, your query should return the following for the above table: Note:
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摘要：Table: Person Table: Address Write a SQL query for a report that provides the following information for each person in the Person table, regardless if
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摘要：X city opened a new cinema, many people would like to go to this cinema. The cinema also gives out a poster indicating the movies’ ratings and descrip
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摘要：There is a table World A country is big if it has an area of bigger than 3 million square km or a population of more than 25 million. Write a SQL solu
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摘要：You are a product manager and currently leading a team to develop a new product. Unfortunately, the latest version of your product fails the quality c
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摘要：概述： 索引（Index）是帮助MySQL高效获取数据的数据结构。 索引是以表列为基础的数据库对象，它保存着表中排序的索引列，并且记录了索引列在数据表中的物理存储位置，实现了表中数据的逻辑排序， 其主要目的是提高数据库系统的性能，加快数据的查询速度和减少系统的响应时间。 在MySQL中，索引是在存储
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摘要：Given a 32-bit signed integer, reverse digits of an integer. Example 1: Example 2: Example 3: Note:Assume we are dealing with an environment which cou
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摘要：直接插入排序： 将一个记录插入到已排序好的有序表中，从而得到一个新，记录数增1的有序表。即：先将序列的第1个记录看成是一个有序的子序列，然后从第2个记录逐个进行插入，直至整个序列有序为止。 时间复杂度：O（n^2） 稳定的 希尔排序： 先将要排序的一组记录按某个增量d（n/2,n为要排序数的个数）分
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摘要：Implement the following operations of a stack using queues. push(x) -- Push element x onto stack. pop() -- Removes the element on top of the stack. to
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摘要：Given a linked list, determine if it has a cycle in it. Follow up:Can you solve it without using extra space? 判断一个链表是否有环 C++（10ms）：
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摘要：We are playing the Guess Game. The game is as follows: I pick a number from 1 to n. You have to guess which number I picked. Every time you guess wron
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摘要：Given an integer, write an algorithm to convert it to hexadecimal. For negative integer, two’s complement method is used. Note: Example 1: Example 2:
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摘要：mv命令用来对文件或目录重新命名，或者将文件从一个目录移到另一个目录中。source表示源文件或目录，target表示目标文件或目录。如果将一个文件移到一个已经存在的目标文件中，则目标文件的内容将被覆盖。 mv命令可以用来将源文件移至一个目标文件中，或将一组文件移至一个目标目录中。源文件被移至目标文
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摘要：rm命令可以删除一个目录中的一个或多个文件或目录，也可以将某个目录及其下属的所有文件及其子目录均删除掉。对于链接文件，只是删除整个链接文件，而原有文件保持不变。
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摘要：Given two lists Aand B, and B is an anagram of A. B is an anagram of A means B is made by randomizing the order of the elements in A. We want to find
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摘要：MySQL中的事务 数据库事务隔离级别 MySQL 的数据存储引擎 MySQL的索引 聚集索引和非聚集索引区别 MySQL索引失效 乐观锁和悲观锁 MySQL中的内连接、外连接、交叉连接 数据库设计三大范式 慢查询日志和profiling explain的使用
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摘要：MySQL的存储引擎 InnoDB： MySQL5.5之后的默认存储引擎。 采用MVCC来支持高并发，并且实现了四个标准的隔离级别(默认可重复读)。 支持事务，支持外键、支持行锁、非锁定读(默认读取操作不会产生锁) 行锁优点是适用于高并发的频繁表修改，高并发是性能优于 MyISAM。缺点是系统消耗较
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摘要：Remove all elements from a linked list of integers that have value val. ExampleGiven: 1 --> 2 --> 6 --> 3 --> 4 --> 5 --> 6, val = 6Return: 1 --> 2 --
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摘要：数据库事务的隔离级别有4个，由低到高依次为Read uncommitted、Read committed、Repeatable read、Serializable 这四个级别可以逐个解决脏读、不可重复读、幻读这几类问题。 READ UNCOMMITTED (未提交读)： 事务中的修改，即使没提交，对
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摘要：Implement the following operations of a queue using stacks. push(x) -- Push element x to the back of queue. pop() -- Removes the element from in front
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摘要：数据库事务 事务指的是满足 ACID 特性的一系列操作。在数据库中，可以通过 Commit 提交一个事务，也可以使用 Rollback 进行回滚。 在 MySQL 中只有使用了 Innodb 数据库引擎的数据库或表才支持事务。 MYSQL 事务处理主要有两种方法： 1、用 BEGIN, ROLLBA
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摘要：You are given a license key represented as a string S which consists only alphanumeric character and dashes. The string is separated into N+1 groups b
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摘要：Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists. Example:
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