davidinga

func binarySearch<Element>(for target: Element, in array: [Element]) -> Int? where Element: Comparable {
    var L = 0
    var R = array.count - 1
    var mid = 0
    
    while L <= R {
        //// Index of middle element.
        mid = L + (R - L) / 2
        
        //// Middle element is target; return it.

davidinga

private func heapify<Element>(_ array: inout [Element], _ count: Int, _ index: Int) where Element: Comparable {
    var largest = index
    let l = 2 * index + 1
    let r = 2 * index + 2
    
    //// Check if left child exists and is greater than parent.
    if l < count && array[index] < array[l] {
        largest = l
    }
    

davidinga

func mergeSort<Element>(array: inout [Element]) where Element: Comparable {
    if array.count > 1 {
        let mid = array.count / 2
        var L = Array(array[..<mid])
        var R = Array(array[mid...])
        
        mergeSort(array: &L)
        mergeSort(array: &R)
        
        var i = 0, j = 0, k = 0

davidinga

extension Array where Element: Comparable {
    private func partition(array: inout [Element], low: Int, high: Int) -> Int {
        let pivot = array[high]
        var i = low - 1
        for j in low..<high {
            if array[j] <= pivot {
                i += 1
                array.swapAt(i, j)
            }
        }

davidinga

extension Array where Element == Int {
    mutating func radixSort() {
        let radix = 10
        var digit = 1
        var done = false
        var unsortedArray = self
        while !done {
            done = true
            /// Counting Sort: Step 1
            /// - Tally each number in count array.

davidinga

func isPalindrome(_ list: DoublyLinkedList<String>) -> Bool {
    // Simple solution. Iterate over linked list and store as string.
    // Uses linear space and time.
    // Then compare string to a reversed string.
    // If equal, then we have a palindrome.
    var node = list.first
    var string = ""
    while node != nil {
        string += String(node!.element)
        node = node!.next

davidinga

func shiftZeros(in array: inout [Int]) {
    var indexToPlaceZero = array.count - 1
    for i in array.indices {
        if array[i] == 0 {
            while array[indexToPlaceZero] == 0, i < indexToPlaceZero {
                indexToPlaceZero -= 1
            }
            array.swapAt(i, indexToPlaceZero)
        }
    }

davidinga

struct HashTableOnlyKeys<Key: Hashable> {
    typealias Element = Key
    typealias List = SinglyLinkedList<Element>
    
    private var table: [List]
    
    private(set) public var count = 0
    
    public var size: Int {
        return table.count

davidinga

public struct Heap<Element> {
    var elements: [Element]
    var priorityFunction: (Element, Element) -> Bool
    
    init(elements: [Element] = [], priorityFunction: @escaping (Element, Element) -> Bool) {
        self.elements = elements
        self.priorityFunction = priorityFunction
        buildHeap()
    }
    

davidinga

extension Array where Element: Comparable {
    
    mutating func insertionSort() {
        
        for (i, element) in self.enumerated() {
            var i = i
            while i > 0 && element < self[i - 1] {
                self[i] = self[i - 1]
                i -= 1
            }