Find the length of the longest substring T of a given string (consists of lowercase letters only) such that every character in T appears no less than k times. Example 1: Input: s = "aaabb", k = 3

本文将演示使用开源类库实现可视化的方式浏览沙箱文件目录。 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

Suppose you have a random list of people standing in a queue. Each person is described by a pair of integers (h, k), where h is the height of the person and k is the number of people in front of this

本文将演示如何创建和解压一个包含密码的压缩包。 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

Given two integers A and B, return any string S such that: S has length A + B and contains exactly A ‘a‘ letters, and exactly B ‘b‘ letters; The substring ‘aaa‘ does not occur in S; The substring ‘bbb

Given an m x n matrix of positive integers representing the height of each unit cell in a 2D elevation map, compute the volume of water it is able to trap after raining.  Note: Both m and n are less t

本文将演示使用Instruments Allocations工具检测应用程序中的内存泄漏问题。 内存溢出 out of memory：是指程序在申请内存时，没有足够的内存空间供其使用，出现out of memory；比如申请了一个integer,但给它存了long才能存下的数，那就是内存溢出。 内存泄露 memory leak：是指程序在申请内存后，无法释放已申请的内存空间，一次内存泄露危害可以忽

Given a non-empty array containing only positive integers, find if the array can be partitioned into two subsets such that the sum of elements in both subsets is equal. Note: Each of the array element

http://www.voidcn.com/article/p-srkqadwc-btx.html   我想要一个简单的按钮(带圆角的按钮),并添加背景.  我已经尝试过两件事情：   1 – 使用圆形按钮图像：这是很好的,直到我需要缩放按钮,这导致圆形部分看起来丑陋. 2 – 扩展按钮并添加颜色 – 但是当我点击按钮时,我有麻烦 – 我希望“推”状态与“常规”状态处于相同的颜色,但情况并非如此.

A gene string can be represented by an 8-character long string, with choices from "A", "C", "G", "T". Suppose we need to investigate about a mutation (mutation from "start" to "end"), where ONE mutati

Given a set of intervals, for each of the interval i, check if there exists an interval j whose start point is bigger than or equal to the end point of the interval i, which can be called that j is on

Given a collection of intervals, find the minimum number of intervals you need to remove to make the rest of the intervals non-overlapping. Note: You may assume the interval‘s end point is always bigg

本文将演示使用单元测试进行邮箱格式的验证。 如果项目中没有引用单元格测试框架， 项目导航区点击选中项目名称，再点击中间列的【+】图标进行添加。 在弹出的模板窗口中，选择单元测试框架模板【iOS Unit Testing Bundle】 ->【Next】->保持默认的选项设置->【Finish】 现在创建一个基于正则表达式的验证类。 在项目文件夹【DemoApp】上点击鼠标右键，弹出右键菜单。 【N

Given a non-empty string check if it can be constructed by taking a substring of it and appending multiple copies of the substring together. You may assume the given string consists of lowercase Engli

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 < 231. Ex

本文将演示如何判断程序是否运行在越狱设备上。 假如产品使用了内购功能，当运行在越狱设备时，可采取一些防御和安全提示措施。 在项目导航区，打开视图控制器的代码文件【ViewController.swift】 越狱设备由于没有沙盒作为保护，黑客可以对系统进行任意的修改， 苹果返回的内购付款凭证有可能是虚假的，所以需要进行越狱设备的检测。 1 import UIKit 2 3 class V

Write a function to check whether an input string is a valid IPv4 address or IPv6 address or neither. IPv4 addresses are canonically represented in dot-decimal notation, which consists of four decimal

本文将演示如何使用Swift实现原生的SHA1加密。 首先创建一个桥接头文件，因为需要使用到OC语言的通用加密解密类库。 在项目文件夹【DemoApp】上点击鼠标右键，弹出右键菜单。 【New File】->【Header File】->【Next】->【Save As】:Header.h->【Create】 在该文件中，添加需要引用到的框架。 1 //添加需要引用到的框架 2 #ifndef

本文将演示如何使用Swift实现原生的MD5加密。 首先创建一个桥接头文件，因为需要使用到OC语言的通用加密解密类库。 在项目文件夹【DemoApp】上点击鼠标右键，弹出右键菜单。 【New File】->【Header File】->【Next】->【Save As】:Header.h->【Create】 在该文件中，添加需要引用到的框架。 1 //添加需要引用到的框架。 2 #ifndef

本文将演示如何编写原生的3DES加密和解密程序。 首先创建一个桥接头文件，因为需要使用到OC语言的通用加密解密类库。 在项目文件夹【DemoApp】上点击鼠标右键，弹出右键菜单。 【New File】->【Header File】->【Next】-> 【Save As】:Header.h->【Create】 在该文件中，添加需要引用到的框架。 1 //添加需要引用到的框架。 2 #ifndef

Given a function rand7 which generates a uniform random integer in the range 1 to 7, write a function rand10 which generates a uniform random integer in the range 1 to 10. Do NOT use system‘s Math.ran

Remember the story of Little Match Girl? By now, you know exactly what matchsticks the little match girl has, please find out a way you can make one square by using up all those matchsticks. You shoul

In the computer world, use restricted resource you have to generate maximum benefit is what we always want to pursue. For now, suppose you are a dominator of m0s and n 1s respectively. On the other ha

Given a list of words (without duplicates), please write a program that returns all concatenated words in the given list of words. A concatenated word is defined as a string that is comprised entirely

For an integer n, we call k>=2 a good base of n, if all digits of n base k are 1. Now given a string representing n, you should return the smallest good base of n in string format.  Example 1: Input:

A magical string S consists of only ‘1‘ and ‘2‘ and obeys the following rules: The string S is magical because concatenating the number of contiguous occurrences of characters ‘1‘ and ‘2‘ generates th

Given an array of scores that are non-negative integers. Player 1 picks one of the numbers from either end of the array followed by the player 2 and then player 1 and so on. Each time a player picks a

We have an array A of integers, and an array queries of queries. For the i-th query val = queries[i][0], index = queries[i][1], we add val to A[index].  Then, the answer to the i-th query is the sum o

Given the root of a binary tree, each node has a value from 0 to 25 representing the letters ‘a‘ to ‘z‘: a value of 0 represents ‘a‘, a value of 1 represents ‘b‘, and so on. Find the lexicographically

Given two lists of closed intervals, each list of intervals is pairwise disjoint and in sorted order. Return the intersection of these two interval lists. (Formally, a closed interval [a, b] (with a <