How to resolve the algorithm Prime triangle step by step in the Swift programming language

Published on 12 May 2024 09:40 PM
#Swift

How to resolve the algorithm Prime triangle step by step in the Swift programming language

Table of Contents

Problem Statement

You will require a function f which when given an integer S will return a list of the arrangements of the integers 1 to S such that g1=1 gS=S and generally for n=1 to n=S-1 gn+gn+1 is prime. S=1 is undefined. For S=2 to S=20 print f(S) to form a triangle. Then again for S=2 to S=20 print the number of possible arrangements of 1 to S meeting these requirements.

Let's start with the solution:

Step by Step solution about How to resolve the algorithm Prime triangle step by step in the Swift programming language

Source code in the swift programming language

import Foundation

func isPrime(_ n: Int) -> Bool {
    guard n > 0 && n < 64 else {
        return false
    }
    return ((UInt64(1) << n) & 0x28208a20a08a28ac) != 0
}

func primeTriangleRow(_ a: inout [Int], start: Int, length: Int) -> Bool {
    if length == 2 {
        return isPrime(a[start] + a[start + 1])
    }
    for i in stride(from: 1, to: length - 1, by: 2) {
        let index = start + i
        if isPrime(a[start] + a[index]) {
            a.swapAt(index, start + 1)
            if primeTriangleRow(&a, start: start + 1, length: length - 1) {
                return true
            }
            a.swapAt(index, start + 1)
        }
    }
    return false
}

func primeTriangleCount(_ a: inout [Int], start: Int, length: Int) -> Int {
    var count = 0
    if length == 2 {
        if isPrime(a[start] + a[start + 1]) {
            count += 1
        }
    } else {
        for i in stride(from: 1, to: length - 1, by: 2) {
            let index = start + i
            if isPrime(a[start] + a[index]) {
                a.swapAt(index, start + 1)
                count += primeTriangleCount(&a, start: start + 1, length: length - 1)
                a.swapAt(index, start + 1)
            }
        }
    }
    return count
}

func printRow(_ a: [Int]) {
    if a.count == 0 {
        return
    }
    print(String(format: "%2d", a[0]), terminator: "")
    for x in a[1...] {
        print(String(format: " %2d", x), terminator: "")
    }
    print()
}

let startTime = CFAbsoluteTimeGetCurrent()

for n in 2...20 {
    var a = Array(1...n)
    if primeTriangleRow(&a, start: 0, length: n) {
        printRow(a)
    }
}
print()

for n in 2...20 {
    var a = Array(1...n)
    if n > 2 {
        print(" ", terminator: "")
    }
    print("\(primeTriangleCount(&a, start: 0, length: n))", terminator: "")
}
print()

let endTime = CFAbsoluteTimeGetCurrent()
print("\nElapsed time: \(endTime - startTime) seconds")

You may also check:How to resolve the algorithm Real constants and functions step by step in the Perl programming language
You may also check:How to resolve the algorithm 24 game/Solve step by step in the ARM Assembly programming language
You may also check:How to resolve the algorithm Hello world/Standard error step by step in the Sather programming language
You may also check:How to resolve the algorithm Factors of a Mersenne number step by step in the Haskell programming language
You may also check:How to resolve the algorithm Terminal control/Dimensions step by step in the Wren programming language