xmhafiz / codility-lesson-swift Goto Github PK

public func solution(_ X : Int, _ Y : Int, _ D : Int) -> Int {
    
    if X == Y { return 0 }
    
    var count = 0
    
    if (Y - X) % D == 0 {
        count = (Y - X) / D
    }
    else {
        count = (Y - X) / D + 1
    }
    
    return count
}

public func solution(_ A : inout [Int]) -> Int {
    
    let n = A.count + 1 // total elements including missing number
    
    // https://math.stackexchange.com/questions/2260/proof-for-formula-for-sum-of-sequence-123-ldotsn
    let sumN = n * (n + 1) / 2 // well know formula to get sums of sequence number from 1 .. N
    
    let sumA = A.reduce(0, +)
    
    return sumN - sumA // subtract and the balance is missing number
}

public func solution(_ X : Int, _ A : inout [Int]) -> Int {
    // write your code in Swift 3.0 (Linux)
    
    var arr = Array(repeating: 0, count: X)
    
    let expectedSum = X * (X + 1) / 2
    
    var sum = 0
    for (i, num) in A.enumerated() {

        if arr[num - 1] == 0 {
            arr[num - 1] = num
            sum += num
            if sum == expectedSum {
                return i
            }
        }
    }
 
    return -1
}