HWS Swift Coding Challenges: Real Problems - Real Solutions

Write a function that accepts a String as its only parameter, and returns true if the string has

only unique letters, taking letter case into account. 

Write a function that accepts a String as its only parameter, and returns true if the string

reads the same when reversed, ignoring case. 

Write a function that accepts two String parameters, and returns true if they contain the same characters in any order taking into account letter case. 

Write your own version of the contains() method on String that ignores letter case, and

without using the existing contains() method. 

Write a function that accepts a string, and returns how many times a specific character appears,

taking case into account. 

Write a function that accepts a string as its input, and returns the same string just with

duplicate letters removed. 

Write a function that returns a string with any consecutive spaces replaced with a single space. 

Write a function that accepts two strings, and returns true if one string is rotation of the other,

taking letter case into account. 

Write a function that returns true if it is given a string that is an English pangram, ignoring

letter case.

Given a string in English, return a tuple containing the number of vowels and consonants. 

Write a function that accepts two strings, and returns true if they are identical in length but

have no more than three different letters, taking case and string order into account. 

Write a function that accepts a string of words with a similar prefix, separated by spaces, and

returns the longest substring that prefixes all words. 

Write a function that accepts a string as input, then returns how often each letter is repeated in

a single run, taking case into account. 

Write a function that prints all possible permutations of a given input string. 

Write a function that returns a string with each of its words reversed but in the original order,

without using a loop. 

Write a function that counts from 1 through 100, and prints “Fizz” if the counter is evenly divisible by 3, “Buzz” if it’s evenly divisible by 5, “Fizz Buzz” if it’s even divisible by three and five, or the counter number for all other cases. 

Write a function that accepts positive minimum and maximum integers, and returns a random

number between those two bounds, inclusive. 

Create a function that accepts positive two integers, and raises the first to the power of the

second.

Swap two positive variable integers, a and b, without using a temporary variable. 

Write a function that accepts an integer as its parameter and returns true if the number is prime. 

Create a function that accepts any positive integer and returns the next highest and next lowest number that has the same number of ones in its binary representation. If either number is not possible, return nil for it. 

Create a function that accepts an unsigned 8-bit integer and returns its binary reverse, padded

so that it holds precisely eight binary digits. 

Write a function that accepts a string and returns true if it contains only numbers, i.e. the digits

0 through 9. 

Given a string that contains both letters and numbers, write a function that pulls out all the

numbers then returns their sum. 

Write a function that returns the square root of a positive integer, rounded down to the nearest

integer, without using sqrt(). 

Create a function that subtracts one positive integer from another, without using - . 

Write a function that accepts a filename on disk, then prints its last N lines in reverse order, all

on a single line separated by commas. 

Write a logging function that accepts accepts a path to a log file on disk as well as a new log message. Your function should open the log file (or create it if it does not already exist), then append the new message to the log along with the current time and date. 

Write a function that returns a URL to the user’s documents directory. 

Write a function that accepts a path to a directory and returns an array of all JPEGs that have

been created in the last 48 hours. 

Write a function that accepts two paths: the first should point to a directory to copy, and the second should be where the directory should be copied to. Return true if the directory and all its contents were copied successfully; false if the copy failed, or the user specified something other than a directory. 

Write a function that accepts a filename on disk, loads it into a string, then returns the frequency of a word in that string, taking letter case into account. How you define “word” is worth considering carefully. 

Write a function that accepts the name of a directory to scan, and returns an array of filenames that appear more than once in that directory or any of its subdirectories. Your function should scan all subdirectories, including subdirectories of subdirectories. 

Write a function that accepts the name of a directory to scan, and returns an array containing

the name of any executable files in there. 

Write a function that accepts a path to a directory, then converts to PNGs any JPEGs it finds in there, leaving the originals intact. If any JPEG can’t be converted the function should just quietly continue. 

Write a function that accepts accepts a path to a log file on disk, and returns how many lines

start with “[ERROR]”. The log file could be as large as 10GB, but may also not exist. 

Write an extension for collections of integers that returns the number of times a specific digit

appears in any of its numbers. 

Write an extension for all collections that returns the N smallest elements as an array, sorted

smallest first, where N is an integer parameter. 

Extend collections with a function that returns an array of strings sorted by their lengths,

longest first. 

Create a function that accepts an array of unsorted numbers from 1 to 100 where zero or more

numbers might be missing, and returns an array of the missing numbers. 

Write an extension to collections that accepts an array of Int and returns the median average,

or nil if there are no values. 

Write an extension for all collections that reimplements the index(of:) method. 

Create a linked list of lowercase English alphabet letters, along with a method that traverses all

nodes and prints their letters on a single line separated by spaces. 

Extend your linked list class with a new method that returns the node at the mid point of the

linked list using no more than one loop. 

Write a new method for your binary search tree that traverses the tree in order, running a closure on each node. 

Write an extension for all collections that reimplements the map() method. 

Write an extension for all collections that reimplements the min() method. 

Create a new data type that models a double-ended queue using generics, or deque. You should be able to push items to the front or back, pop them from the front or back, and get the number of items. 

Write a function that accepts a variadic array of integers and return the sum of all numbers that

appear an even number of times. 

Write a function that accepts an array of positive and negative numbers and returns a closed range containing the position of the contiguous positive numbers that sum to the highest value, or nil if nothing were found. 

Expand your code from challenge 43 so that it has a reversed() method that returns a copy

of itself in reverse. 

Write one function that sums an array of numbers. The array might contain all integers, all

doubles, or all floats. 

Your job is to write a function that accepts your linked list as its parameter, and returns the node at the start of the loop, i.e. the one that is linked back to. 

Create a binary search tree data structure that can be initialized from an unordered array of

comparable values, then write a method that returns whether the tree is balanced. 

Create an extension for arrays that sorts them using the bubble sort algorithm. 

Create an extension for arrays that sorts them using the insertion sort algorithm. 

Write a function that accepts two values and returns true if they are isomorphic. That is, each

part of the value must map to precisely one other, but that might be itself. 

Write a function that accepts a string containing the characters (, [, {, <, >, }, ], and ) in any arrangement and frequency. It should return true if the brackets are opened and closed in the correct order, and if all brackets are closed. Any other input should false. 

Create an extension for arrays that sorts them using the quicksort algorithm. 

Create a function that detects whether either player has won in a game of Tic-Tac-Toe. 

Write a function that returns an array of prime numbers from 2 up to but excluding N, taking

care to be as efficient as possible.

Write a function that accepts an array of CGPoint pairs, and returns an array of the angles

between each point pair. Return the angles in degrees, where 0 or 360 is straight up. 

There are M different ways you can place N queens on an NxN chessboard so that none of them are able to capture others. Write a function that calculates them all and prints them to the screen as a visual board layout, and returns the number of solutions it found.