Question

How to generate an N-digit integer random number in Swift

Answer 1

import Foundation

/// Generate an n-digit random number.
/// For n=1, range is 0–9; for n>1, ensures no leading zeros.
func generateNDigitNumber(_ n: Int) throws -> Int {
    guard n >= 1 else {
        throw NSError(domain: "RandomNDigits", code: 1,
                      userInfo: [NSLocalizedDescriptionKey: "n must be a positive integer (>= 1)."])
    }

    let lowerBound = (n > 1) ? Int(pow(10.0, Double(n - 1))) : 0
    let upperBound = Int(pow(10.0, Double(n))) - 1

    return Int.random(in: lowerBound...upperBound)
}

do {
    print(try generateNDigitNumber(1))
    print(try generateNDigitNumber(4))
    print(try generateNDigitNumber(10))
} catch {
    print("Error:", error.localizedDescription)
}



/*
run:

2
8625
7464190715

*/

 

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