There are n bulbs that are initially off. You first turn on all the bulbs. Then, you turn off every second bulb. On the third round, you toggle every third bulb (turning on if it‘s off or turning off

Given a string which contains only lowercase letters, remove duplicate letters so that every letter appear once and only once. You must make sure your result is the smallest in lexicographical order a

Given two arrays of length m and n with digits 0-9 representing two numbers. Create the maximum number of length k <= m + n from digits of the two. The relative order of the digits from the same array

You are given an integer array nums and you have to return a new countsarray. The counts array has the property where counts[i] is the number of smaller elements to the right of nums[i]. Example: Inpu

Given a string array words, find the maximum value of length(word[i]) * length(word[j]) where the two words do not share common letters. You may assume that each word will contain only lower case lett

Given a singly linked list, group all odd nodes together followed by the even nodes. Please note here we are talking about the node number and not the value in the nodes. You should try to do it in pl

Given an unsorted array nums, reorder it such that nums[0] < nums[1] > nums[2] < nums[3].... Example 1: Input: Output: One possible answer is .nums = [1, 5, 1, 1, 6, 4][1, 4, 1, 5, 1, 6] Example 2:

Given an integer matrix, find the length of the longest increasing path. From each cell, you can either move to four directions: left, right, up or down. You may NOT move diagonally or move outside of

You are given coins of different denominations and a total amount of money amount. Write a function to compute the fewest number of coins that you need to make up that amount. If that amount of money

Given an integer array nums, return the number of range sums that lie in [lower, upper] inclusive. Range sum S(i, j) is defined as the sum of the elements in numsbetween indices i and j (i ≤ j), inclu

Given a sorted positive integer array nums and an integer n, add/patch elements to the array such that any number in range [1, n] inclusive can be formed by the sum of some elements in the array. Retu

Given a positive integer n, break it into the sum of at least two positive integers and maximize the product of those integers. Return the maximum product you can get. Example 1: Input: 2 Output: 1 E

Given a non negative integer number num. For every numbers i in the range 0 ≤ i ≤ num calculate the number of 1‘s in their binary representation and return them as an array. Example 1: Input: 2 Outpu

The thief has found himself a new place for his thievery again. There is only one entrance to this area, called the "root." Besides the root, each house has one and only one parent house. After a tour

We have a list of points on the plane.  Find the K closest points to the origin (0, 0). (Here, the distance between two points on a plane is the Euclidean distance.) You may return the answer in any o

You are given an integer array A.  From some starting index, you can make a series of jumps.  The (1st, 3rd, 5th, ...) jumps in the series are called odd numbered jumps, and the (2nd, 4th, 6th, ...) j

本文将演示如何给视图添加Align(对齐)和Fill(填充的约束以及Label的约束。 锚点默认位于视图中心点的位置。 首先确保在项目中已经安装了所需的第三方库。 点击【Podfile】,查看安装配置文件。 1 platform :ios, ‘12.0’ 2 use_frameworks! 3 4 target ‘DemoApp‘ do 5 source ‘https://git

先介绍一下Swift String 自身的方法，后面介绍简单的使用方法 1、截取前面5个字符 let substr = string.prefix(5)   2、截取后面5个字符 let substr = string.suffix(5)   3、获取下标 N 到 M 的字符（0 <= N < M <= string.count） // let string = "12345678" let

https://swift.libhunt.com/categories/688-events 29 Events libraries and projects ORDERED BY POPULARITY ORDER BY DEV ACTIVITY  ReactiveCocoa   10.0   7.3  Objective-C ReactiveCocoa (RAC) is a Cocoa fra

swift 日出日落时间，真个也是从OC转过来的，可能不是很好，但是能用。 import UIKit class PGSun: NSObject { struct Sunriseset { var sunrise = "07:00" // 日出 var sunset = "18:30" // 日落 init(sunrise:String,

Given a non-empty 2D matrix matrix and an integer k, find the max sum of a rectangle in the matrix such that its sum is no larger than k. Example: Input: matrix = [[1,0,1],[0,-2,3]], k = 2 Output: 2 E

共享可执行文件 iOS 有沙箱机制，不能跨App间共享共态库，但Apple开放了App Extension，可以在App和Extension间共间动态库（这也许是Apple开放动态链接库的唯一原因了）。 http://blog.lanvige.com/2015/01/04/library-vs-framework-in-ios/?utm_source=tuicool&utm_medium=refe

Given a n x n matrix where each of the rows and columns are sorted in ascending order, find the kth smallest element in the matrix. Note that it is the kth smallest element in the sorted order, not th

Given a nested list of integers represented as a string, implement a parser to deserialize it. Each element is either an integer, or a list -- whose elements may also be integers or other lists. Note:

使用案例 ``` extension UITextView {     ```     private struct RuntimeKey {         static let hw_placeholderLabelKey = UnsafeRawPointer.init(bitPattern: "hw_placeholderLabelKey".hashValue)         /// ..

On a 2-dimensional grid, there are 4 types of squares: 1 represents the starting square.  There is exactly one starting square. 2 represents the ending square.  There is exactly one ending square. 0 r

There is a list of sorted integers from 1 to n. Starting from left to right, remove the first number and every other number afterward until you reach the end of the list. Repeat the previous step agai

Given an encoded string, return it‘s decoded string. The encoding rule is: k[encoded_string], where the encoded_stringinside the square brackets is being repeated exactly k times. Note that kis guaran

本文将演示使用开源类库实现CoreData数据的增删改查。 首先确保在项目中已经安装了所需的第三方库。 点击【Podfile】,查看安装配置文件。 1 platform :ios, ‘12.0‘ 2 use_frameworks! 3 4 target ‘AERecordDemo‘ do 5 source ‘https://github.com/CocoaPods/Specs.g

本文将演示使用开源类库对SQLite数据库进行高效操作。 首先确保在项目中已经安装了所需的第三方库。 点击【Podfile】,查看安装配置文件。 1 platform :ios, ‘12.0’ 2 use_frameworks! 3 4 target ‘DemoApp‘ do 5 source ‘https://github.com/CocoaPods/Specs.git‘ 6