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iOS

Jannik Spiessens
Jannik Spiessens
13,229 Points
Posted by Jannik Spiessens
Jannik Spiessens
13,229 Points

Highest Prime Factor challenge

I am challenging myself to make a function in swift that receives an integer and returns the highest prime factor of that integer. I currently have something like that and it works but whenever I try it whit higher numbers, e.g. 100,000,000, it takes to long and my computer crashes. I was wondering if someone could give me some tips to speed up the function.

func getLargestPrimeFast(n: Int) -> Int? {
    var p = 1
    var pDiv = 0
    do {
        if n % p == 0 {
            pDiv = n / p
            for var i = 2;i <= pDiv - 1;i++ {
                if pDiv % i == 0 {
                    break
                }
                if i == pDiv - 1 {
                    return pDiv
                }
            }
            p++
        } else {
            p++
        }
    } while p < n
    return nil
}

1 Answer

Stephen Whitfield
Stephen Whitfield
16,771 Points
Stephen Whitfield
Stephen Whitfield
16,771 Points

https://developer.apple.com/library/ios/documentation/General/Reference/SwiftStandardLibraryReference/NumericTypes.html

Try making that Int an Int32.

Jannik Spiessens
Jannik Spiessens
13,229 Points
Jannik Spiessens
Jannik Spiessens
13,229 Points

Does this make the function faster or just more suitable for the task?