10. Prime and composite numbers. MinPerimeterRectangle.swift

import Foundation
import Glibc

// Solution @ Sergey Leschev, Belarusian State University

// 10. Prime and composite numbers. MinPerimeterRectangle.

// An integer N is given, representing the area of some rectangle.
// The area of a rectangle whose sides are of length A and B is A * B, and the perimeter is 2 * (A + B).

// The goal is to find the minimal perimeter of any rectangle whose area equals N. The sides of this rectangle should be only integers.

// For example, given integer N = 30, rectangles of area 30 are:
// (1, 30), with a perimeter of 62,
// (2, 15), with a perimeter of 34,
// (3, 10), with a perimeter of 26,
// (5, 6), with a perimeter of 22.

// Write a function:
// class Solution { public int solution(int N); }
// that, given an integer N, returns the minimal perimeter of any rectangle whose area is exactly equal to N.

// For example, given an integer N = 30, the function should return 22, as explained above.

// Write an efficient algorithm for the following assumptions:
// N is an integer within the range [1..1,000,000,000].

public func solution(_ N: Int) -> Int {
    let side = Int(sqrt(Double(N)).rounded(FloatingPointRoundingRule.up))
        
    for i in stride(from: side, to: 0, by: -1) where N % i == 0 { return (i + N / i) * 2 }
    return -1
}