Question

How to find the prime factors of a number in Swift

Answer 1

import Foundation

func getPrimeFactors(_ n: Int) -> [Int] {
    var factors: [Int] = []
    var number = n
    var divisor = 2

    while number >= 2 {
        if number % divisor == 0 {
            factors.append(divisor)
            number /= divisor
        } else {
            divisor += 1
        }
    }

    return factors
}

let testNumbers = [124, 288, 1288]
for n in testNumbers {
    let result = getPrimeFactors(n).map { String($0) }.joined(separator: " x ")
    print("\(n) = \(result)")
}



/*
run:

124 = 2 x 2 x 31
288 = 2 x 2 x 2 x 2 x 2 x 3 x 3
1288 = 2 x 2 x 2 x 7 x 23

*/

 

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