Add 1 number in an array - Geeks for geeks

addOneNumber.swift

/* Test Cases
 Input: [1, 2, 3, 4]
 Output: [1, 2, 3, 5]
 
 Input: [1, 2, 9, 9]
 Output: [1, 3, 0, 0]
 
 Input: [9, 9, 9, 9]
 Output: [1, 0, 0, 0]
 
 Input: []
 Output: [1]
 */
func addOneNumber(_ array: [Int]) -> [Int] {
    
    // if empty input
    if array.isEmpty {
        return [1]
    }
    
    var carry = 1
    var result: [Int] = array.map {
        let sum = $0 + carry
        
        if sum == 10 {
            carry = 1
            return 0
        } else {
            carry = 0
            return sum
        }
    }

    // Corner Case:
    // if all of the values are 9
    if carry != 0 {
        result.append(carry)
        let lastIndex = result.count-1
        result.swapAt(0, lastIndex)
    }
    
    return result
}