Question

How to check if an array is all increasing or decreasing and the gap between numbers is 1, 2 or 3 in Swift

Answer 1

import Foundation

func isArraySortedAndValidGap(_ arr: [Int]) -> Bool {
    if arr.count < 2 { return true }

    let increasing = arr[1] > arr[0]
    for i in 1..<arr.count {
        let diff = abs(arr[i] - arr[i - 1])
        if diff < 1 || diff > 3 {
            return false
        }
        if (increasing && arr[i] <= arr[i - 1]) || (!increasing && arr[i] >= arr[i - 1]) {
            return false
        }
    }
    return true
}

let arr1 = [1, 2, 3, 5, 8, 11, 14, 15]
print(isArraySortedAndValidGap(arr1)) 

let arr2 = [15, 14, 11, 8, 5, 3, 2, 1]
print(isArraySortedAndValidGap(arr2))

let arr3 = [1, 2, 300, 5, 8, 11, 14, 15]
print(isArraySortedAndValidGap(arr3)) 



/*
run:

true
true
false

*/

 

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