import kotlin.math.abs
/**
* Finds the maximum distance (absolute index difference) between two numbers in an array.
*
* @param arr The input integer array (IntArray).
* @param num1 The first target number.
* @param num2 The second target number.
* @return The maximum absolute index difference, or null if either number is missing.
*/
fun maxDistanceBetweenNumbers(arr: IntArray, num1: Int, num2: Int): Int? {
// Variables to track the first and last occurrences of both numbers
var first1 = -1
var last1 = -1
var first2 = -1
var last2 = -1
// Single pass through the array: O(N) time complexity, O(1) space complexity
arr.forEachIndexed { index, current ->
if (current == num1) {
if (first1 == -1) {
first1 = index // Record the first time num1 appears
}
last1 = index // Continuously update the last time num1 appears
} else if (current == num2) {
if (first2 == -1) {
first2 = index // Record the first time num2 appears
}
last2 = index // Continuously update the last time num2 appears
}
}
// Edge case: If either number is not present in the array, return null
if (first1 == -1 || first2 == -1) {
return null
}
// The maximum distance is always between the outermost boundaries of the two sets:
// 1. Distance between the first occurrence of num1 and the last occurrence of num2
// 2. Distance between the last occurrence of num1 and the first occurrence of num2
val dist1 = abs(first1 - last2)
val dist2 = abs(last1 - first2)
return maxOf(dist1, dist2)
}
fun main() {
// --- Example Usage ---
val array = intArrayOf(2, 3, 7, 3, 3, 4, 8, 8, 8, 11, 9, 1, 3)
val number1 = 3
val number2 = 8
val result = maxDistanceBetweenNumbers(array, number1, number2)
if (result != null) {
println("The maximum distance between $number1 and $number2 is: $result")
} else {
println("One or both numbers ($number1, $number2) were not found in the array.")
}
}
/*
run:
The maximum distance between 3 and 8 is: 7
*/
