摘要：
Suppose an array sorted in ascending order is rotated at some pivot unknown to you beforehand. (i.e., [0,1,2,4,5,6,7] might become [4,5,6,7,0,1,2]). F 阅读全文
随笔档案-2018年08月
[LeetCode] 153. Find Minimum in Rotated Sorted Array_Medium tag: Binary Search
2018-08-31 06:53 by Johnson_强生仔仔, 264 阅读, 收藏, 编辑
摘要：
Suppose an array sorted in ascending order is rotated at some pivot unknown to you beforehand. (i.e., [0,1,2,4,5,6,7] might become [4,5,6,7,0,1,2]). F 阅读全文
[LeetCode] 69. Sqrt(x)_Easy tag: Binary Search
2018-08-31 06:35 by Johnson_强生仔仔, 198 阅读, 收藏, 编辑
摘要：
Implement int sqrt(int x). Compute and return the square root of x, where x is guaranteed to be a non-negative integer. Since the return type is an in 阅读全文
[LeetCode] 240. Search a 2D Matrix II_Medium tag: Binary Search
2018-08-31 06:21 by Johnson_强生仔仔, 280 阅读, 收藏, 编辑
摘要：
Write an efficient algorithm that searches for a value in an m x n matrix. This matrix has the following properties: Integers in each row are sorted i 阅读全文
[LeetCode] 74. Search a 2D Matrix_Medium tag: Binary Search
2018-08-30 11:08 by Johnson_强生仔仔, 233 阅读, 收藏, 编辑
摘要：
Write an efficient algorithm that searches for a value in an m x n matrix. This matrix has the following properties: Integers in each row are sorted f 阅读全文
[LeetCode] 162. Find Peak Element(852. Peak Index in a Mountain Array)_Medium tag: Binary Search
2018-08-29 11:39 by Johnson_强生仔仔, 192 阅读, 收藏, 编辑
摘要：
A peak element is an element that is greater than its neighbors. Given an input array nums, where nums[i] ≠ nums[i+1], find a peak element and return 阅读全文
[LeetCode] 278. First Bad Version_Easy tag: Binary Search
2018-08-29 11:19 by Johnson_强生仔仔, 151 阅读, 收藏, 编辑
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 阅读全文
[LeetCode] 35. Search Insert Position_Easy tag: Binary Search
2018-08-29 10:34 by Johnson_强生仔仔, 213 阅读, 收藏, 编辑
摘要：
Given a sorted array and a target value, return the index if the target is found. If not, return the index where it would be if it were inserted in or 阅读全文
[LeetCode] 34. Find First and Last Position of Element in Sorted Array == [LintCode] 61. Search for a Range_Easy tag: Binary Search
2018-08-29 10:06 by Johnson_强生仔仔, 267 阅读, 收藏, 编辑
摘要：
Description Given a sorted array of n integers, find the starting and ending position of a given target value. If the target is not found in the array 阅读全文
[LeetCode] 374. Guess Number Higher or Lower_Easy tag: Binary Search
2018-08-29 07:22 by Johnson_强生仔仔, 214 阅读, 收藏, 编辑
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 阅读全文
[LeetCode] 704. Binary Search_Easy tag: Binary Search
2018-08-29 06:52 by Johnson_强生仔仔, 220 阅读, 收藏, 编辑
摘要：
Given a sorted (in ascending order) integer array nums of n elements and a target value, write a function to search target in nums. If target exists, 阅读全文
[LeetCode] questions conclusion_ Binary Search
2018-08-29 06:49 by Johnson_强生仔仔, 343 阅读, 收藏, 编辑
摘要：
Binary Search T(n) = T(n/2) + O(1) => T(n) = O(lg n) proof: 如果能用iterable , 就用while loop, 可以防止用recursion的时候stack overflow( process in Linux is 8Mb), st 阅读全文
[LeetCode] 610. Triangle Judgement_Easy tag: SQL
2018-08-28 23:59 by Johnson_强生仔仔, 380 阅读, 收藏, 编辑
摘要：
A pupil Tim gets homework to identify whether three line segments could possibly form a triangle. However, this assignment is very heavy because there 阅读全文
[LeetCode] 613. Shortest Distance in a Line_Easy tag: SQL
2018-08-28 23:53 by Johnson_强生仔仔, 393 阅读, 收藏, 编辑
摘要：
Table point holds the x coordinate of some points on x-axis in a plane, which are all integers. Write a query to find the shortest distance between tw 阅读全文
[LeetCode] 422. Valid Word Square_Easy
2018-08-28 23:42 by Johnson_强生仔仔, 267 阅读, 收藏, 编辑
摘要：
Given a sequence of words, check whether it forms a valid word square. A sequence of words forms a valid word square if the kth row and column read th 阅读全文
[LeetCode] 492. Construct the Rectangle_Easy tag: Math
2018-08-28 23:20 by Johnson_强生仔仔, 171 阅读, 收藏, 编辑
摘要：
For a web developer, it is very important to know how to design a web page's size. So, given a specific rectangular web page’s area, your job by now i 阅读全文
[LeetCode] 619. Biggest Single Number_Easy tag: SQL
2018-08-28 23:13 by Johnson_强生仔仔, 298 阅读, 收藏, 编辑
摘要：
Table number contains many numbers in column num including duplicated ones.Can you write a SQL query to find the biggest number, which only appears on 阅读全文
[LeetCode] 584. Find Customer Referee_Easy tag: SQL
2018-08-28 23:04 by Johnson_强生仔仔, 376 阅读, 收藏, 编辑
摘要：
Given a table customer holding customers information and the referee. + + + + | id | name | referee_id| + + + + | 1 | Will | NULL | | 2 | Jane | NULL 阅读全文
[LeetCode] 603. Consecutive Available Seats_Easy tag: SQL
2018-08-28 21:57 by Johnson_强生仔仔, 638 阅读, 收藏, 编辑
摘要：
Several friends at a cinema ticket office would like to reserve consecutive available seats.Can you help to query all the consecutive available seats 阅读全文
[LeetCode] 607. Sales Person_Easy tag: SQL
2018-08-28 21:40 by Johnson_强生仔仔, 629 阅读, 收藏, 编辑
摘要：
Description Given three tables: salesperson, company, orders.Output all the names in the table salesperson, who didn’t have sales to company 'RED'. Ex 阅读全文
[LeetCode] 506. Relative Ranks_Easy tag: Sort
2018-08-28 12:23 by Johnson_强生仔仔, 149 阅读, 收藏, 编辑
摘要：
Given scores of N athletes, find their relative ranks and the people with the top three highest scores, who will be awarded medals: "Gold Medal", "Sil 阅读全文
[LeetCode] 747. Largest Number At Least Twice of Others_Easy
2018-08-28 12:08 by Johnson_强生仔仔, 162 阅读, 收藏, 编辑
摘要：
In a given integer array nums, there is always exactly one largest element. Find whether the largest element in the array is at least twice as much as 阅读全文
[LeetCode] 840. Magic Squares In Grid_Easy
2018-08-28 12:02 by Johnson_强生仔仔, 325 阅读, 收藏, 编辑
摘要：
A 3 x 3 magic square is a 3 x 3 grid filled with distinct numbers from 1 to 9 such that each row, column, and both diagonals all have the same sum. Gi 阅读全文
[LeetCode] 405. Convert a Number to Hexadecimal_Easy tag: Bit Manipulation
2018-08-28 08:27 by Johnson_强生仔仔, 164 阅读, 收藏, 编辑
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: 阅读全文
[LeetCode] 276. Paint Fence_Easy tag: Dynamic Programming
2018-08-28 08:14 by Johnson_强生仔仔, 235 阅读, 收藏, 编辑
摘要：
There is a fence with n posts, each post can be painted with one of the k colors. You have to paint all the posts such that no more than two adjacent 阅读全文
[LeetCode] 762. Prime Number of Set Bits in Binary Representation_Easy
2018-08-28 00:55 by Johnson_强生仔仔, 198 阅读, 收藏, 编辑
摘要：
Given two integers L and R, find the count of numbers in the range [L, R] (inclusive) having a prime number of set bits in their binary representation 阅读全文
[LeetCode] 693. Binary Number with Alternating Bits_Easy
2018-08-28 00:42 by Johnson_强生仔仔, 240 阅读, 收藏, 编辑
摘要：
Given a positive integer, check whether it has alternating bits: namely, if two adjacent bits will always have different values. Example 1: Input: 5 O 阅读全文
[LeetCode] 434. Number of Segments in a String_Easy
2018-08-28 00:38 by Johnson_强生仔仔, 218 阅读, 收藏, 编辑
摘要：
Count the number of segments in a string, where a segment is defined to be a contiguous sequence of non-space characters. Please note that the string 阅读全文
[LeetCode] 872. Leaf-Similar Trees_Easy tag: DFS
2018-08-28 00:01 by Johnson_强生仔仔, 217 阅读, 收藏, 编辑
摘要：
Consider all the leaves of a binary tree. From left to right order, the values of those leaves form a leaf value sequence. For example, in the given t 阅读全文
[LeetCode] 598. Range Addition II_Easy tag: Math
2018-08-27 23:48 by Johnson_强生仔仔, 187 阅读, 收藏, 编辑
摘要：
做个基本思路可以用 brute force, 但时间复杂度较高. 因为起始值都为0, 所以肯定是左上角的重合的最小的长方形就是结果, 所以我们求x, y 的最小值, 最后返回x*y. Code T: O(m*n) S: O(1) 阅读全文
[LeetCode] 661. Image Smoother_Easy
2018-08-27 12:07 by Johnson_强生仔仔, 157 阅读, 收藏, 编辑
摘要：
Given a 2D integer matrix M representing the gray scale of an image, you need to design a smoother to make the gray scale of each cell becomes the ave 阅读全文
[LeetCode] 20. Valid Parentheses_Easy tag: Stack
2018-08-25 00:55 by Johnson_强生仔仔, 225 阅读, 收藏, 编辑
摘要：
Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid. An input string is valid if: No 阅读全文
[LeetCode] 367. Valid Perfect Square_Easy tag:Math
2018-08-21 13:32 by Johnson_强生仔仔, 210 阅读, 收藏, 编辑
摘要：
Given a positive integer num, write a function which returns True if num is a perfect square else False. Note: Do not use any built-in library functio 阅读全文
[LeetCode] 868. Binary Gap_Easy
2018-08-20 10:43 by Johnson_强生仔仔, 209 阅读, 收藏, 编辑
摘要：
Given a positive integer N, find and return the longest distance between two consecutive 1's in the binary representation of N. If there aren't two co 阅读全文
[LeetCode] 577. Employee Bonus_Easy tag: SQL
2018-08-20 10:34 by Johnson_强生仔仔, 272 阅读, 收藏, 编辑
摘要：
Select all employee's name and bonus whose bonus is < 1000. Table:Employee Table: Bonus Example ouput: # 不能直接用JOIN, 相当于inner join, 如果bonus没有的, 那么就没有了, 阅读全文
[LeetCode] 860. Lemonade Change_Easy tag: Greedy
2018-08-20 10:21 by Johnson_强生仔仔, 217 阅读, 收藏, 编辑
摘要：
At a lemonade stand, each lemonade costs $5. Customers are standing in a queue to buy from you, and order one at a time (in the order specified by bil 阅读全文
[LeetCode] 859. Buddy Strings_Easy
2018-08-20 09:59 by Johnson_强生仔仔, 249 阅读, 收藏, 编辑
摘要：
Given two strings A and B of lowercase letters, return true if and only if we can swap two letters in A so that the result equals B. Example 1: Input: 阅读全文
[LeetCode] 876. Middle of the Linked List_Easy tag: Linked List ** slow, fast pointers
2018-08-20 09:37 by Johnson_强生仔仔, 237 阅读, 收藏, 编辑
摘要：
Given a non-empty, singly linked list with head node head, return a middle node of linked list. If there are two middle nodes, return the second middl 阅读全文
[LeetCode] 788. Rotated Digits_Easy tag: **Dynamic Programming
2018-08-20 09:29 by Johnson_强生仔仔, 235 阅读, 收藏, 编辑
摘要：
基本思路建一个helper function, 然后从1-N依次判断是否为good number, 注意判断条件为没有3,4,7 的数字,并且至少有一个2,5,6,9, 否则的话数字就一样了, 比如88, 18等. Improve: 利用DP去判断, 时间和空间都能降为O(lgn) Code T: 阅读全文
[LeetCode] 620. Not Boring Movies_Easy tag: SQL
2018-08-20 09:17 by Johnson_强生仔仔, 218 阅读, 收藏, 编辑
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 阅读全文
[LeetCode] 408. Valid Word Abbreviation_Easy
2018-08-20 09:11 by Johnson_强生仔仔, 229 阅读, 收藏, 编辑
摘要：
Given a non-empty string s and an abbreviation abbr, return whether the string matches with the given abbreviation. A string such as "word" contains o 阅读全文
[LeetCode] 504. Base 7_Easy tag: Math
2018-08-20 08:47 by Johnson_强生仔仔, 180 阅读, 收藏, 编辑
摘要：
Given an integer, return its base 7 string representation. Example 1: Example 2: Note: The input will be in range of [-1e7, 1e7]. 不停除以7, 然后把余数放到ans里面, 阅读全文
[LeetCode] 830. Positions of Large Groups_Easy tag: Two Pointers
2018-08-20 03:56 by Johnson_强生仔仔, 187 阅读, 收藏, 编辑
摘要：
In a string S of lowercase letters, these letters form consecutive groups of the same character. For example, a string like S = "abbxxxxzyy" has the g 阅读全文
[LeetCode] 586. Customer Placing the Largest Number of Orders_Easy tag;SQL
2018-08-20 03:36 by Johnson_强生仔仔, 842 阅读, 收藏, 编辑
摘要：
Query the customer_number from the orders table for the customer who has placed the largest number of orders. It is guaranteed that exactly one custom 阅读全文
[LeetCode] 824. Goat Latin_Easy
2018-08-20 03:14 by Johnson_强生仔仔, 138 阅读, 收藏, 编辑
摘要：
A sentence S is given, composed of words separated by spaces. Each word consists of lowercase and uppercase letters only. We would like to convert the 阅读全文
[LeetCode] 596. Classes More Than 5 Students_Easy tag:SQL
2018-08-20 03:03 by Johnson_强生仔仔, 181 阅读, 收藏, 编辑
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 阅读全文
[LeetCode] 744. Find Smallest Letter Greater Than Target_Easy tag: Binary Search
2018-08-20 02:46 by Johnson_强生仔仔, 175 阅读, 收藏, 编辑
摘要：
Given a list of sorted characters letters containing only lowercase letters, and given a target letter target, find the smallest element in the list t 阅读全文
[LeetCode] 414. Third Maximum Number_Easy
2018-08-20 02:33 by Johnson_强生仔仔, 185 阅读, 收藏, 编辑
摘要：
Given a non-empty array of integers, return the third maximum number in this array. If it does not exist, return the maximum number. The time complexi 阅读全文
[LeetCode] 696. Count Binary Substrings_Easy
2018-08-20 02:09 by Johnson_强生仔仔, 254 阅读, 收藏, 编辑
摘要：
利用group, 将每个连着的0或者1计数并且append进入group里面, 然后再将group里面的两两比较, 得到min, 并且加入到ans即可. T: O(n) S: O(n) 比较好理解 improve: 思路相同, 用pre和cur去将space节省到O(1) Code 1) T: O( 阅读全文
[LeetCode] 709. To Lower Case_Easy
2018-08-20 01:47 by Johnson_强生仔仔, 228 阅读, 收藏, 编辑
摘要：
Implement function ToLowerCase() that has a string parameter str, and returns the same string in lowercase. Example 1: Input: "Hello" Output: "hello" 阅读全文
[LeetCode] 581. Shortest Unsorted Continuous Subarray_Easy tag: Sort, Stack
2018-08-20 01:37 by Johnson_强生仔仔, 198 阅读, 收藏, 编辑
摘要：
Given an integer array, you need to find one continuous subarray that if you only sort this subarray in ascending order, then the whole array will be 阅读全文
[LeetCode] 849. Maximize Distance to Closest Person_Easy tag: BFS
2018-08-19 05:35 by Johnson_强生仔仔, 223 阅读, 收藏, 编辑
摘要：
In a row of seats, 1 represents a person sitting in that seat, and 0 represents that the seat is empty. There is at least one empty seat, and at least 阅读全文
[LeetCode] 455. Assign Cookies_Easy tag: Sort
2018-08-19 05:10 by Johnson_强生仔仔, 248 阅读, 收藏, 编辑
摘要：
Assume you are an awesome parent and want to give your children some cookies. But, you should give each child at most one cookie. Each child i has a g 阅读全文
[LeetCode] 884. Uncommon Words from Two Sentences_Easy tag: Hash Table
2018-08-19 04:54 by Johnson_强生仔仔, 348 阅读, 收藏, 编辑
摘要：
We are given two sentences A and B. (A sentence is a string of space separated words. Each word consists only of lowercase letters.) A word is uncommo 阅读全文
[LeetCode] 566. Reshape the Matrix_Easy
2018-08-19 04:50 by Johnson_强生仔仔, 230 阅读, 收藏, 编辑
摘要：
In MATLAB, there is a very useful function called 'reshape', which can reshape a matrix into a new one with different size but keep its original data. 阅读全文
[LeetCode] 643. Maximum Average Subarray I_Easy tag: Dynamic Programming(Sliding windows)
2018-08-18 12:38 by Johnson_强生仔仔, 241 阅读, 收藏, 编辑
摘要：
Given an array consisting of n integers, find the contiguous subarray of given length k that has the maximum average value. And you need to output the 阅读全文
[LeetCode] 441. Arranging Coins_Easy tag: Math
2018-08-18 12:13 by Johnson_强生仔仔, 193 阅读, 收藏, 编辑
摘要：
You have a total of n coins that you want to form in a staircase shape, where every k-th row must have exactly k coins. Given n, find the total number 阅读全文
[LeetCode] 867. Transpose Matrix_Easy
2018-08-18 11:55 by Johnson_强生仔仔, 163 阅读, 收藏, 编辑
摘要：
Given a matrix A, return the transpose of A. The transpose of a matrix is the matrix flipped over it's main diagonal, switching the row and column ind 阅读全文
[LeetCode] 58. Length of Last Word_Easy tag: String
2018-08-18 11:38 by Johnson_强生仔仔, 150 阅读, 收藏, 编辑
摘要：
Given a string s consists of upper/lower-case alphabets and empty space characters ' ', return the length of last word in the string. If the last word 阅读全文
[LeetCode] 182. Duplicate Emails_Easy tag: SQL
2018-08-18 11:19 by Johnson_强生仔仔, 125 阅读, 收藏, 编辑
摘要：
Write a SQL query to find all duplicate emails in a table named Person. + + + | Id | Email | + + + | 1 | a@b.com | | 2 | c@d.com | | 3 | a@b.com | + + 阅读全文
[LeetCode] 476. Number Complement_Easy tag: Bit Manipulation
2018-08-18 11:14 by Johnson_强生仔仔, 174 阅读, 收藏, 编辑
摘要：
这个题目思路就是比如101 的结果是010, 可以从111^101 来得到, 那么我们就需要知道刚好比101多一位的1000, 所以利用 while i <= num : i <<= 1, 去得到1000, 然后-1, 便得到111, 再跟num ^, 也就是异或即可. Code 阅读全文
[LeetCode] 844. Backspace String Compare_Easy tag: Stack, Two pointers
2018-08-18 10:52 by Johnson_强生仔仔, 262 阅读, 收藏, 编辑
摘要：
Given two strings S and T, return if they are equal when both are typed into empty text editors. # means a backspace character. Example 1: Input: S = 阅读全文
[LeetCode] 728. Self Dividing Numbers_Easy tag: Math
2018-08-18 06:03 by Johnson_强生仔仔, 172 阅读, 收藏, 编辑
摘要：
A self-dividing number is a number that is divisible by every digit it contains. For example, 128 is a self-dividing number because 128 % 1 == 0, 128 阅读全文
[LeetCode] 197. Rising Temperature_Easy tag: SQL
2018-08-18 05:54 by Johnson_强生仔仔, 221 阅读, 收藏, 编辑
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 阅读全文
[LeetCode] 496. Next Greater Element I_Easy tag: Stack
2018-08-18 05:44 by Johnson_强生仔仔, 186 阅读, 收藏, 编辑
摘要：
You are given two arrays (without duplicates) nums1 and nums2 where nums1’s elements are subset of nums2. Find all the next greater numbers for nums1' 阅读全文
[LeetCode] 225. Implement Stack using Queues_Easy tag: Design
2018-08-18 05:30 by Johnson_强生仔仔, 306 阅读, 收藏, 编辑
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 阅读全文
[LeetCode] 532. K-diff Pairs in an Array_Easy tag: Hash Table
2018-08-17 11:44 by Johnson_强生仔仔, 226 阅读, 收藏, 编辑
摘要：
Given an array of integers and an integer k, you need to find the number of unique k-diff pairs in the array. Here a k-diff pair is defined as an inte 阅读全文
[LeetCode] 605. Can Place Flowers_Easy
2018-08-17 11:27 by Johnson_强生仔仔, 231 阅读, 收藏, 编辑
摘要：
Suppose you have a long flowerbed in which some of the plots are planted and some are not. However, flowers cannot be planted in adjacent plots - they 阅读全文
[LeetCode] 183. Customers Who Never Order_Easy tag: SQL
2018-08-17 11:09 by Johnson_强生仔仔, 185 阅读, 收藏, 编辑
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 阅读全文
[LeetCode] 821. Shortest Distance to a Character_Easy tag: BFS
2018-08-17 10:58 by Johnson_强生仔仔, 241 阅读, 收藏, 编辑
摘要：
Given a string S and a character C, return an array of integers representing the shortest distance from the character C in the string. Example 1: Note 阅读全文
[LeetCode] 796. Rotate String_Easy **KMP
2018-08-17 10:40 by Johnson_强生仔仔, 189 阅读, 收藏, 编辑
摘要：
We are given two strings, A and B. A shift on A consists of taking string A and moving the leftmost character to the rightmost position. For example, 阅读全文
[LeetCode] 168. Excel Sheet Column Title_Easy tag: Math
2018-08-17 10:02 by Johnson_强生仔仔, 277 阅读, 收藏, 编辑
摘要：
Given a positive integer, return its corresponding column title as appear in an Excel sheet. For example: Example 1: Example 2: Example 3: 这个题目实际上就想用2 阅读全文
[LeetCode] 836. Rectangle Overlap_Easy
2018-08-17 06:01 by Johnson_强生仔仔, 212 阅读, 收藏, 编辑
摘要：
A rectangle is represented as a list [x1, y1, x2, y2], where (x1, y1) are the coordinates of its bottom-left corner, and (x2, y2) are the coordinates 阅读全文
[LeetCode] 345. Reverse Vowels of a String_Easy tag:Two Pointers
2018-08-17 03:37 by Johnson_强生仔仔, 189 阅读, 收藏, 编辑
摘要：
Write a function that takes a string as input and reverse only the vowels of a string. Example 1: Example 2: Input: "leetcode" Output: "leotcede" Exam 阅读全文
[LeetCode] 196. Delete Duplicate Emails_Easy tag: SQL
2018-08-17 00:46 by Johnson_强生仔仔, 188 阅读, 收藏, 编辑
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. + + + | Id | Ema 阅读全文
[LeetCode] 832. Flipping an Image_Easy
2018-08-17 00:35 by Johnson_强生仔仔, 230 阅读, 收藏, 编辑
摘要：
Given a binary matrix A, we want to flip the image horizontally, then invert it, and return the resulting image. To flip an image horizontally means t 阅读全文
[LeetCode] 190. Reverse Bits_Easy tag: Bit Manipulation
2018-08-16 23:13 by Johnson_强生仔仔, 177 阅读, 收藏, 编辑
摘要：
Reverse bits of a given 32 bits unsigned integer. Example: Follow up:If this function is called many times, how would you optimize it? 这个题目就是利用Bit Man 阅读全文
[LeetCode] 243. Shortest Word Distance_Easy
2018-08-16 12:08 by Johnson_强生仔仔, 195 阅读, 收藏, 编辑
摘要：
Given a list of words and two words word1 and word2, return the shortest distance between these two words in the list. Example:Assume that words = ["p 阅读全文
[LeetCode] 256. Paint House_Easy tag: Dynamic Programming
2018-08-16 11:17 by Johnson_强生仔仔, 211 阅读, 收藏, 编辑
摘要：
There are a row of n houses, each house can be painted with one of the three colors: red, blue or green. The cost of painting each house with a certai 阅读全文
[LeetCode] 172. Factorial Trailing Zeroes_Easy tag: Math
2018-08-16 10:46 by Johnson_强生仔仔, 199 阅读, 收藏, 编辑
摘要：
Given an integer n, return the number of trailing zeroes in n!. Example 1: Example 2: Note: Your solution should be in logarithmic time complexity. 思路 阅读全文
[LeetCode] 181. Employees Earning More Than Their Managers_Easy tag: SQL
2018-08-16 10:24 by Johnson_强生仔仔, 163 阅读, 收藏, 编辑
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 阅读全文
[LeetCode] 252. Meeting Rooms_Easy tag: Sort
2018-08-16 10:11 by Johnson_强生仔仔, 207 阅读, 收藏, 编辑
摘要：
Given an array of meeting time intervals consisting of start and end times [[s1,e1],[s2,e2],...] (si < ei), determine if a person could attend all mee 阅读全文
[LeetCode] 232. Implement Queue using Stacks_Easy tag: Design
2018-08-16 09:49 by Johnson_强生仔仔, 241 阅读, 收藏, 编辑
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 阅读全文
[LeetCode] 724. Find Pivot Index_Easy tag: Dynamic Programming
2018-08-16 00:49 by Johnson_强生仔仔, 201 阅读, 收藏, 编辑
摘要：
Given an array of integers nums, write a method that returns the "pivot" index of this array. We define the pivot index as the index where the sum of 阅读全文
[LeetCode] 364. Nested List Weight Sum II_Medium tag:DFS
2018-08-16 00:21 by Johnson_强生仔仔, 270 阅读, 收藏, 编辑
摘要：
Given a nested list of integers, return the sum of all integers in the list weighted by their depth. Each element is either an integer, or a list -- w 阅读全文
[LeetCode] 339. Nested List Weight Sum_Easy tag:DFS
2018-08-15 23:50 by Johnson_强生仔仔, 282 阅读, 收藏, 编辑
摘要：
Given a nested list of integers, return the sum of all integers in the list weighted by their depth. Each element is either an integer, or a list -- w 阅读全文
[LeetCode] 628. Maximum Product of Three Numbers_Easy
2018-08-15 12:22 by Johnson_强生仔仔, 185 阅读, 收藏, 编辑
摘要：
Given an integer array, find three numbers whose product is maximum and output the maximum product. Example 1: Input: [1,2,3] Output: 6 Example 2: Inp 阅读全文
[LeetCode] 438. Find All Anagrams in a String_Easy
2018-08-15 11:14 by Johnson_强生仔仔, 144 阅读, 收藏, 编辑
摘要：
438. Find All Anagrams in a String 438. Find All Anagrams in a String 438. Find All Anagrams in a String 438. Find All Anagrams in a String Descriptio 阅读全文
[LeetCode] 804. Unique Morse Code Words_Easy tag: Hash Table
2018-08-15 05:10 by Johnson_强生仔仔, 157 阅读, 收藏, 编辑
摘要：
International Morse Code defines a standard encoding where each letter is mapped to a series of dots and dashes, as follows: "a"maps to ".-", "b" maps 阅读全文
[LeetCode] 717. 1-bit and 2-bit Characters_Easy
2018-08-15 04:56 by Johnson_强生仔仔, 187 阅读, 收藏, 编辑
摘要：
We have two special characters. The first character can be represented by one bit 0. The second character can be represented by two bits (10 or 11). N 阅读全文
[LeetCode] 383. Ransom Note_Easy tag: Hash Table
2018-08-15 00:45 by Johnson_强生仔仔, 160 阅读, 收藏, 编辑
摘要：
Given an arbitrary ransom note string and another string containing letters from all the magazines, write a function that will return true if the rans 阅读全文
[LeetCode] 203. Remove Linked List Elements_Easy tag: Linked LIst
2018-08-15 00:38 by Johnson_强生仔仔, 154 阅读, 收藏, 编辑
摘要：
Remove all elements from a linked list of integers that have value val. Example: Input: 1->2->6->3->4->5->6, val = 6 Output: 1->2->3->4->5 Remove all 阅读全文
[LeetCode] 680. Valid Palindrome II_Easy tag: Two Pointers
2018-08-15 00:24 by Johnson_强生仔仔, 213 阅读, 收藏, 编辑
摘要：
Given a non-empty string s, you may delete at most one character. Judge whether you can make it a palindrome. Example 1: Example 2: Note: 题目思路就是正常的用tw 阅读全文
[LeetCode] 69. Sqrt(x)_Easy tag: Binary Search
2018-08-14 23:53 by Johnson_强生仔仔, 169 阅读, 收藏, 编辑
摘要：
Implement int sqrt(int x). Compute and return the square root of x, where x is guaranteed to be a non-negative integer. Since the return type is an in 阅读全文
[LeetCode] 627. Swap Salary_Easy tag: SQL
2018-08-14 23:33 by Johnson_强生仔仔, 210 阅读, 收藏, 编辑
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 阅读全文
[LeetCode] 697. Degree of an Array_Easy tag: Hash Table
2018-08-13 05:46 by Johnson_强生仔仔, 142 阅读, 收藏, 编辑
摘要：
Given a non-empty array of non-negative integers nums, the degree of this array is defined as the maximum frequency of any one of its elements. Your t 阅读全文
[LeetCode] 443. String Compression_Easy tag:String
2018-08-13 05:22 by Johnson_强生仔仔, 151 阅读, 收藏, 编辑
摘要：
Given an array of characters, compress it in-place. The length after compression must always be smaller than or equal to the original array. Every ele 阅读全文
[LeetCode] 415. Add Strings_Easy tag: String
2018-08-13 04:21 by Johnson_强生仔仔, 256 阅读, 收藏, 编辑
摘要：
Given two non-negative integers num1 and num2 represented as string, return the sum of num1 and num2. Note: 这个题目跟[LeetCode] 67. Add Binary_Easy tag: S 阅读全文
[LeetCode] 67. Add Binary_Easy tag: String
2018-08-13 04:05 by Johnson_强生仔仔, 199 阅读, 收藏, 编辑
摘要：
Given two binary strings, return their sum (also a binary string). The input strings are both non-empty and contains only characters 1 or 0. Example 1 阅读全文
[LeetCode] 557. Reverse Words in a String III_Easy tag: String
2018-08-13 03:39 by Johnson_强生仔仔, 216 阅读, 收藏, 编辑
摘要：
Given a string, you need to reverse the order of characters in each word within a sentence while still preserving whitespace and initial word order. E 阅读全文
[LeetCode] 176. Second Highest Salary_Easy tag: SQL
2018-08-12 05:28 by Johnson_强生仔仔, 180 阅读, 收藏, 编辑
摘要：
Write a SQL query to get the second highest salary from the Employee table. + + + | Id | Salary | + + + | 1 | 100 | | 2 | 200 | | 3 | 300 | + + + For 阅读全文
[LeetCode] 88. Merge Sorted Array_Easy tag: Two Pointers
2018-08-12 05:21 by Johnson_强生仔仔, 201 阅读, 收藏, 编辑
摘要：
Given two sorted integer arrays nums1 and nums2, merge nums2 into nums1 as one sorted array. Note: The number of elements initialized in nums1 and num 阅读全文
[LeetCode] 258. Add Digits_Easy tag: Math
2018-08-11 11:59 by Johnson_强生仔仔, 160 阅读, 收藏, 编辑
摘要：
Given a non-negative integer num, repeatedly add all its digits until the result has only one digit. Example: Follow up:Could you do it without any lo 阅读全文
[LeetCode] 193. Valid Phone Numbers_Easy tag: Bash
2018-08-11 05:32 by Johnson_强生仔仔, 226 阅读, 收藏, 编辑
摘要：
Given a text file file.txt that contains list of phone numbers (one per line), write a one liner bash script to print all valid phone numbers. You may 阅读全文
[LeetCode] 38. Count and Say_Easy
2018-08-11 05:13 by Johnson_强生仔仔, 178 阅读, 收藏, 编辑
摘要：
The count-and-say sequence is the sequence of integers with the first five terms as following: 1 is read off as "one 1" or 11.11 is read off as "two 1 阅读全文
[LeetCode] 561. Array Partition I_Easy tag: Sort
2018-08-11 04:39 by Johnson_强生仔仔, 213 阅读, 收藏, 编辑
摘要：
Given an array of 2n integers, your task is to group these integers into n pairs of integer, say (a1, b1), (a2, b2), ..., (an, bn) which makes sum of 阅读全文
[LeetCode] 595. Big Countries_Easy tag: SQL
2018-08-11 04:28 by Johnson_强生仔仔, 226 阅读, 收藏, 编辑
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 阅读全文
[LeetCode] 195. Tenth Line_Easy tag: Bash
2018-08-11 04:21 by Johnson_强生仔仔, 215 阅读, 收藏, 编辑
摘要：
Given a text file file.txt, print just the 10th line of the file. Example: Assume that file.txt has the following content: Line 1 Line 2 Line 3 Line 4 阅读全文
[LeetCode] 237. Delete Node in a Linked List_Easy tag: Linked List
2018-08-11 00:44 by Johnson_强生仔仔, 220 阅读, 收藏, 编辑
摘要：
Write a function to delete a node (except the tail) in a singly linked list, given only access to that node. Given linked list -- head = [4,5,1,9], wh 阅读全文
[LeetCode] 458. Poor Pigs_Easy tag: Math
2018-08-10 23:59 by Johnson_强生仔仔, 147 阅读, 收藏, 编辑
摘要：
There are 1000 buckets, one and only one of them contains poison, the rest are filled with water. They all look the same. If a pig drinks that poison 阅读全文
[LeetCode] 292. Nim Game_Easy tag: Math
2018-08-10 23:19 by Johnson_强生仔仔, 216 阅读, 收藏, 编辑
摘要：
You are playing the following Nim Game with your friend: There is a heap of stones on the table, each time one of you take turns to remove 1 to 3 ston 阅读全文
[LeetCode] 1. Two Sum_Easy tag: Hash Table
2018-08-10 12:16 by Johnson_强生仔仔, 263 阅读, 收藏, 编辑
摘要：
Given an array of integers, return indices of the two numbers such that they add up to a specific target. You may assume that each input would have ex 阅读全文
[LeetCode] 559. Maximum Depth of N-ary Tree_Easy tag: DFS
2018-08-09 09:00 by Johnson_强生仔仔, 269 阅读, 收藏, 编辑
摘要：
Given a n-ary tree, find its maximum depth. The maximum depth is the number of nodes along the longest path from the root node down to the farthest le 阅读全文
[LeetCode] 310. Minimum Height Trees_Medium tag: BFS
2018-08-09 04:31 by Johnson_强生仔仔, 183 阅读, 收藏, 编辑
摘要：
For a undirected graph with tree characteristics, we can choose any node as the root. The result graph is then a rooted tree. Among all possible roote 阅读全文
[LeetCode] 787. Cheapest Flights Within K Stops_Medium tag: Dynamic Programming, BFS, Heap
2018-08-09 00:00 by Johnson_强生仔仔, 265 阅读, 收藏, 编辑
摘要：
There are n cities connected by m flights. Each fight starts from city u and arrives at v with a price w. Now given all the cities and fights, togethe 阅读全文
[LeetCode] 490. The Maze_Medium tag: BFS/DFS
2018-08-08 04:34 by Johnson_强生仔仔, 356 阅读, 收藏, 编辑
摘要：
There is a ball in a maze with empty spaces and walls. The ball can go through empty spaces by rolling up, down, left or right, but it won't stop roll 阅读全文
[LeetCode] 129. Sum Root to Leaf Numbers_Medium tag: DFS
2018-08-08 00:40 by Johnson_强生仔仔, 284 阅读, 收藏, 编辑
摘要：
Given a binary tree containing digits from 0-9 only, each root-to-leaf path could represent a number. An example is the root-to-leaf path 1->2->3 whic 阅读全文
[LeetCode] 78. Subsets tag: backtracking
2018-08-08 00:26 by Johnson_强生仔仔, 270 阅读, 收藏, 编辑
摘要：
Given a set of distinct integers, nums, return all possible subsets (the power set). Note: The solution set must not contain duplicate subsets. Exampl 阅读全文
[LeetCode] 130. Surrounded Regions_Medium tag: DFS/BFS
2018-08-08 00:09 by Johnson_强生仔仔, 248 阅读, 收藏, 编辑
摘要：
Given a 2D board containing 'X' and 'O' (the letter O), capture all regions surrounded by 'X'. A region is captured by flipping all 'O's into 'X's in 阅读全文
[LeetCode] 99. Recover Binary Search Tree_Hard_Inorder traversal
2018-08-07 23:37 by Johnson_强生仔仔, 200 阅读, 收藏, 编辑
摘要：
Two elements of a binary search tree (BST) are swapped by mistake. Recover the tree without changing its structure. Example 1: Input: [1,3,null,null,2 阅读全文
[LeetCode] 100. Same Tree_Easy tag: DFS
2018-08-07 04:31 by Johnson_强生仔仔, 187 阅读, 收藏, 编辑
摘要：
Given two binary trees, write a function to check if they are the same or not. Two binary trees are considered the same if they are structurally ident 阅读全文
[LeetCode] All questions numbers conclusion 所有题目题号
2018-08-07 00:50 by Johnson_强生仔仔, 520 阅读, 收藏, 编辑
摘要：
Note: 后面数字n表明刷的第n + 1遍, 如果题目有**, 表明有待总结 Conclusion questions: [LeetCode] questions conclustion_BFS, DFS LeetCode questions conclustion_Path in Tree [L 阅读全文
[LeetCode] 110. Balanced Binary Tree_Easy tag: DFS
2018-08-07 00:49 by Johnson_强生仔仔, 227 阅读, 收藏, 编辑
摘要：
Given a binary tree, determine if it is height-balanced. For this problem, a height-balanced binary tree is defined as: a binary tree in which the dep 阅读全文
[LeetCode] questions conclusion_ Dynamic Programming
2018-08-06 23:49 by Johnson_强生仔仔, 337 阅读, 收藏, 编辑
摘要：
Questions: [LeetCode] 198. House Robber _Easy tag: Dynamic Programming [LeetCode] 221. Maximal Square _ Medium Tag: Dynamic Programming [LeetCode] 62. 阅读全文
[LeetCode] 111. Minimum Depth of Binary Tree_Easy tag:DFS
2018-08-06 23:19 by Johnson_强生仔仔, 207 阅读, 收藏, 编辑
摘要：
Given a binary tree, find its minimum depth. The minimum depth is the number of nodes along the shortest path from the root node down to the nearest l 阅读全文
[LeetCode] 122. Best Time to Buy and Sell Stock II_Easy tag: Dynamic Programming
2018-08-03 23:51 by Johnson_强生仔仔, 264 阅读, 收藏, 编辑
摘要：
Say you have an array for which the ith element is the price of a given stock on day i. Design an algorithm to find the maximum profit. You may comple 阅读全文
[LeetCode] 121. Best Time to Buy and Sell Stock_Easy tag: Dynamic Programming
2018-08-03 23:27 by Johnson_强生仔仔, 220 阅读, 收藏, 编辑
摘要：
Say you have an array for which the ith element is the price of a given stock on day i. If you were only permitted to complete at most one transaction 阅读全文
[LeetCode] 674. Longest Continuous Increasing Subsequence_Easy Dynamic Programming
2018-08-02 09:18 by Johnson_强生仔仔, 237 阅读, 收藏, 编辑
摘要：
Given an unsorted array of integers, find the length of longest continuous increasing subsequence (subarray). Example 1: Example 2: Note: Length of th 阅读全文
[LeetCode] 152. Maximum Product Subarray_Medium tag: Dynamic Programming
2018-08-02 05:46 by Johnson_强生仔仔, 227 阅读, 收藏, 编辑
摘要：
Given an integer array nums, find the contiguous subarray within an array (containing at least one number) which has the largest product. Example 1: I 阅读全文
[LeetCode] 53. Maximum Subarray_Easy tag: Dynamic Programming
2018-08-02 04:39 by Johnson_强生仔仔, 325 阅读, 收藏, 编辑
摘要：
Given an integer array nums, find the contiguous subarray (containing at least one number) which has the largest sum and return its sum. Example: 3.2) 阅读全文
[LeetCode] 312. Burst Balloons_hard tag: 区间Dynamic Programming
2018-08-01 05:07 by Johnson_强生仔仔, 298 阅读, 收藏, 编辑
摘要：
Given n balloons, indexed from 0 to n-1. Each balloon is painted with a number on it represented by array nums. You are asked to burst all the balloon 阅读全文
[LeetCode] 877. Stone Game == [LintCode] 396. Coins in a Line 3_hard tag: 区间Dynamic Programming, 博弈
2018-08-01 01:24 by Johnson_强生仔仔, 859 阅读, 收藏, 编辑
摘要：
Alex and Lee play a game with piles of stones. There are an even number of piles arranged in a row, and each pile has a positive integer number of sto 阅读全文
