1346. Check If N and Its Double Exist

[kevin373738]

 public func checkIfExist(_ arr: [Int]) -> Bool {
        guard !arr.isEmpty else { return false }
        var set: Set<Int>  = []
        for i in 0..<arr.count {
            
            if set.contains(arr[i] * 2) || (arr[i] % 2 == 0 && set.contains(arr[i] / 2)) {
                // If either the double or half of the current element exists in the set, return true
                return true
            }
            
            set.insert(arr[i])
            
        }
        
//        for i in 0..<arr.count {
//            let num = 2*arr[i]
//            results.insert(num)
//        }
//        for value in arr {
//            if results.contains(value) {
//                return true
//            }
//        }
        return false
      }