Given a set of numbers, determine if there is a pair that equals a given sum.

main.swift

//func hasPairWithSum(_ arr: [Int], _ sum: Int) -> Bool {
//
//    for i in 0..<arr.count {
//        for j in i + 1..<arr.count {
//            if arr[i] + arr[j] == sum {
//                return true
//            }
//        }
//    }
//    return false
//}

func hasPairWithSum(_ arr: [Int], _ sum: Int) -> Bool {
    var comp = Set<Int>()
    for value in arr {
        if comp.contains(value) {
            return true
        }
        comp.insert(sum-value)
    }
    return false
}


hasPairWithSum([1,2,4,9], 8) //false
hasPairWithSum([1,2,4,4], 8) //true
hasPairWithSum([1,2,5,3], 8) //true