## C, search, interpolation_search.c

``````#include <stdio.h>

/* By comparison, binary search always chooses the middle of the remaining
* search space, discarding one half or the other, depending on the comparison
* between the key found at the estimated position and the key sought. The
* remaining search space is reduced to the part before or after the estimated
* position. The linear search uses equality only as it compares elements
* one-by-one from the start, ignoring any sorting. On average the interpolation
* search makes about log(log(n)) comparisons (if the elements are uniformly
* distributed), where n is the number of elements to be searched. In the worst
* case (for instance where the numerical values of the keys increase
* exponentially) it can make up to O(n) comparisons. In
* interpolation-sequential search, interpolation is used to find an item near
* the one being searched for, then linear search is used to find the exact
* item. */

int interpolationSearch(int arr[], int n, int key)
{
int low = 0, high = n - 1;
while (low <= high && key >= arr[low] && key <= arr[high])
{
/* Calculate the nearest posible position of key */
int pos =
low + ((key - arr[low]) * (high - low)) / (arr[high] - arr[low]);
if (key > arr[pos])
low = pos + 1;
else if (key < arr[pos])
high = pos - 1;
else /* Found */
return pos;
}
return -1;
}

int main()
{
int x;
int arr[] = {10, 12, 13, 16, 18, 19, 20, 21, 22, 23, 24, 33, 35, 42, 47};
int n = sizeof(arr) / sizeof(arr[0]);

printf("Array: ");
for (int i = 0; i < n; i++) printf("%d ", arr[i]);
printf("\nEnter the number to be searched: ");
scanf("%d", &x); /* Element to be searched */

int index = interpolationSearch(arr, n, x);

/* If element was found */
if (index != -1)
printf("Element found at position: %d\n", index);
else