Project Euler in Swift #1 for Medium

1.swift

let filtered = (1..<1000).filter {
    $0 % 3 == 0 || $0 % 5 == 0
}
filtered.reduce(0, combine: +)

2.swift

extension Int {
    func divisibleBy(num: Int) -> Bool {
        return num % self == 0
    }
}

3.swift

func satisfyOne<T>(target: T, rules: [T -> Bool]) -> Bool {
    for rule in rules {
        if rule(target) {
            return true
        }
    }
    return false
}

4.swift

func sumOfMultiples(numbers: [Int], divisibles: [Int -> Bool]) -> Int {
    return numbers.filter { satisfyOne($0, rules: divisibles) }.reduce(0, combine: +)
}

sumOfMultiples(Array(1..<1000), divisibles: [3.divisibleBy, 5.divisibleBy])

5.swift

sumOfMultiples(Array(1..<1000), divisibles: [3.divisibleBy, 5.divisibleBy, 7.divisibleBy])

6.swift

func sumOfMultiples(max: Int, divisor: Int) -> Int {
    let n = max / divisor
    return n * (n + 1) / 2 * divisor
}

func sumOfMultiples(max: Int, divisor1: Int, divisor2: Int) -> Int {
    return sumOfMultiples(max, divisor: divisor1)
        + sumOfMultiples(max, divisor: divisor2)
        - sumOfMultiples(max, divisor: divisor1 * divisor2)
}

sumOfMultiples(999, divisor1: 3, divisor2: 5)

7.swift

let max = 999
sumOfMultiples(max, divisor: 3) + sumOfMultiples(max, divisor: 5) + sumOfMultiples(max, divisor: 7) - sumOfMultiples(max, divisor: 15) - sumOfMultiples(max, divisor: 21) - sumOfMultiples(max, divisor: 35) + sumOfMultiples(max, divisor: 105)