#include <stdio.h>
#include <limits.h>
/*
* Find the minimum distance between two numbers in an array.
*
* Parameters:
* arr - input array
* size - number of elements in the array
* number1 - first target number
* number2 - second target number
*
* Returns:
* Minimum distance between number1 and number2.
* Returns -1 if no valid pair exists.
*
* Time Complexity: O(n)
* Space Complexity: O(1)
*/
int min_distance(const int arr[], int size, int number1, int number2)
{
int lastIndex = -1;
int minDistance = INT_MAX;
for (int i = 0; i < size; ++i)
{
/* Process only occurrences of the target values */
if (arr[i] == number1 || arr[i] == number2) {
/*
* If we've previously seen one of the target values
* and the current value is the other target value,
* update the minimum distance.
*/
if (lastIndex != -1 && arr[i] != arr[lastIndex]) {
int distance = i - lastIndex;
if (distance < minDistance) {
minDistance = distance;
}
}
/* Remember the most recent occurrence */
lastIndex = i;
}
}
return (minDistance == INT_MAX) ? -1 : minDistance;
}
int main(void)
{
const int arr[] = {2, 3, 7, 3, 3, 4, 8, 8, 8, 11, 9, 1, 3};
const int size = sizeof(arr) / sizeof(arr[0]);
int result = min_distance(arr, size, 3, 8);
if (result >= 0) {
printf("Minimum distance between 3 and 8: %d\n", result);
}
else {
printf("No valid pair found.\n");
}
return 0;
}
/*
run:
Minimum distance between 3 and 8: 2
*/
