/**
* Finds the maximum distance (absolute index difference) between two numbers in an array.
*
* @param arr - The input array of numbers.
* @param num1 - The first target number.
* @param num2 - The second target number.
* @returns The maximum absolute index difference, or null if either number is missing.
*/
function maxDistanceBetweenNumbers(arr: number[], num1: number, num2: number): number | null {
// Variables to track the first and last occurrences of both numbers
let first1: number = -1;
let last1: number = -1;
let first2: number = -1;
let last2: number = -1;
// Single pass through the array: O(N) time complexity, O(1) space complexity
for (let i: number = 0; i < arr.length; i++) {
const current: number = arr[i];
if (current === num1) {
if (first1 === -1) {
first1 = i; // Record the first time num1 appears
}
last1 = i; // Continuously update the last time num1 appears
}
else if (current === num2) {
if (first2 === -1) {
first2 = i; // Record the first time num2 appears
}
last2 = i; // Continuously update the last time num2 appears
}
}
// Edge case: If either number is not present in the array, distance cannot be calculated
if (first1 === -1 || first2 === -1) {
return null;
}
// The maximum distance will always be 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
return Math.max(
Math.abs(first1 - last2),
Math.abs(last1 - first2)
);
}
// --- Example Usage ---
const array: number[] = [2, 3, 7, 3, 3, 4, 8, 8, 8, 11, 9, 1, 3];
const number1: number = 3;
const number2: number = 8;
const result: number | null = maxDistanceBetweenNumbers(array, number1, number2);
console.log(`The maximum distance between ${number1} and ${number2} is: ${result}`);
/*
run:
The maximum distance between 3 and 8 is: 7
*/
