Given s1, s2, s3, find whether s3 is formed by the interleaving of s1 and s2. Example 1: Input: s1 = "aabcc", s2 = "dbbca", s3 = "aadbbcbcac" Output: true Example 2: Input: s1 = "aabcc", s2 = "dbbc

Given n, how many structurally unique BST‘s (binary search trees) that store values 1 ... n? Example: Input: 3 Output: 5 Explanation: Given n = 3, there are a total of 5 unique BST‘s: 1

Given a binary tree, return the level order traversal of its nodes‘ values. (ie, from left to right, level by level). For example: Given binary tree [3,9,20,null,null,15,7], 3 / 9 20 /

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]   1   /  3     2 Output: [3,1,null,nu

You have an array of logs.  Each log is a space delimited string of words. For each log, the first word in each log is an alphanumeric identifier.  Then, either: Each word after the identifier will co

函数类型 每个函数都有一个特定的函数类型，由函数的参数类型和返回类型组成。 例如： 1 func addTwoInts(_ a: Int, _ b: Int) -> Int { 2 return a + b 3 } 4 5 func multiplyTwoInts(_ a: Int, _ b: Int) -> Int { 6 return a * b 7 } 这个例子

Attributes provide more information about a declaration or type. There are two kinds of attributes in Swift, those that apply to declarations and those that apply to types. You specify an attribute by

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 that surrounded region. Example: X X X X X O O X

Given a string S that only contains "I" (increase) or "D" (decrease), let N = S.length. Return any permutation A of [0, 1, ..., N] such that for all i = 0, ..., N-1: If S[i] == "I", then A[i] < A[i+1]

Given an array A of integers, return true if and only if it is a valid mountain array. Recall that A is a mountain array if and only if: A.length >= 3 There exists some i with 0 < i < A.length - 1 suc

2014年06月03日凌晨。Apple刚刚公布了Swift编程语言。本文从其公布的书籍《The Swift Programming Language》中摘录和提取而成。 希望对各位的iOS&OSX开发有所帮助。 前言 在这里我觉得有必要提一下Brec Victor的Inventing on Principle。Swift编程环境的大部分概念都源自于Brec这个演讲。 接下来进入正题。 Swift是

On a 2D plane, we place stones at some integer coordinate points.  Each coordinate point may have at most one stone. Now, a move consists of removing a stone that shares a column or row with another s

Given two sequences pushed and popped with distinct values, return true if and only if this could have been the result of a sequence of push and pop operations on an initially empty stack.  Example 1:

You have an initial power P, an initial score of 0 points, and a bag of tokens. Each token can be used at most once, has a value token[i], and has potentially two ways to use it. If we have at least t

Given an array A of strings, find any smallest string that contains each string in A as a substring. We may assume that no string in A is substring of another string in A. Example 1: Input: ["alex","l

　　核心代码　　　　section.removeAll {baseRow in　　　　if let habitRow = baseRow as? HabitRow{　　　　let idxPath = habitRow.indexPath!　　　　return willRemoveIdxPaths.contains(idxPath)　　　　}　　　　return false　　　　以上代码片段的功能

Design and implement a data structure for Least Recently Used (LRU) cache. It should support the following operations: get and put. get(key) - Get the value (will always be positive) of the key if the

Given n points on a 2D plane, find the maximum number of points that lie on the same straight line. Example 1: Input: [[1,1],[2,2],[3,3]] Output: 3 Explanation: ^ | |        o |     o |  o   +

Evaluate the value of an arithmetic expression in Reverse Polish Notation. Valid operators are +, -, *, /. Each operand may be an integer or another expression. Note: Division between two integers sho

For a binary tree T, we can define a flip operation as follows: choose any node, and swap the left and right child subtrees. A binary tree X is flip equivalent to a binary tree Y if and only if we can

In a deck of cards, every card has a unique integer.  You can order the deck in any order you want. Initially, all the cards start face down (unrevealed) in one deck. Now, you do the following steps r

Given an array of 4 digits, return the largest 24 hour time that can be made. The smallest 24 hour time is 00:00, and the largest is 23:59.  Starting from 00:00, a time is larger if more time has elap

1 public class DJSet 2 { 3 var upper:[Int] 4 var w:[Int] 5 6 init(_ n:Int) 7 { 8 upper = [Int](repeating:-1,count:n) 9 w = [Int](repeating:0,count:

Given a non-empty array of unique positive integers A, consider the following graph: There are A.length nodes, labelled A[0] to A[A.length - 1]; There is an edge between A[i] and A[j] if and only if A

Given an integer array nums, find the contiguous subarray within an array (containing at least one number) which has the largest product. Example 1: Input: [2,3,-2,4] Output: Explanation: [2,3] has

Design a stack that supports push, pop, top, and retrieving the minimum element in constant time. push(x) -- Push element x onto stack. pop() -- Removes the element on top of the stack. top() -- Get t

The API: int read4(char *buf) reads 4 characters at a time from a file. The return value is the actual number of characters read. For example, it returns 3 if there is only 3 characters left in the fi

访问控制（Access Control） 访问控制可以限定其他源文件或模块中的代码对你的代码的访问级别。这个特性可以让我们隐藏代码的一些实现细节，并且可以指定一些代码和访问和使用的优先接口。 你可以明确地给单个类型（类、结构体、枚举）设置访问级别，也可以给这些类型的属性、方法、构造器、下标等设置访问级别。协议也可以被限定在一定的范围内使用，包括协议里的全局常量、变量和函数。 Swift 不仅提供了

1 初始加入设备后、上传Object的详细流程  前几篇博客中，我们讲到环的基本原理即详细的实现过程，加入我们在初始创建Ring是执行例如以下几条命令： ?swift-ring-builder object.builder create 5 3 1   ? swift-ring-builder  object.builder  add z1-127.0.0.1:6010/sdb1 100    

In an alien language, surprisingly they also use english lowercase letters, but possibly in a different order. The order of the alphabet is some permutation of lowercase letters. Given a sequence of w