/* Program to demonstrate Interpolation search */

/* We assume that the array is sorted in ascending order */

#include  <stdio.h>
#include  <conio.h>

int  interpolation(int  x[ ], int  n, int  key) ;

void  main()
{
    int  i, n, x[20], key ;
    clrscr() ;
    printf("Enter the number of elements: ") ;
    scanf("%d",&n) ;
    printf("Enter the elements:\n") ;
    for(i=0 ; i<n ; i++)
        scanf("%d",&x[i]) ;
    printf("Enter the element to be searched: ") ;
    scanf("%d",&key) ;
    i=interpolation(x,n,key) ;
    if(i==-1)
        printf("%d not found.", key) ;
    else
        printf("%d found at position %d.", key,i) ;
    getch() ;
}

int  interpolation(int  x[ ], int  n, int  key)
{
    int low,high,mid;
    low=0;
    high=n-1;
    while(low<=high)
        {
            /* ONLY DIFFERENCE BETWEEN BINARY AND INTERPOLATION SEARCH */
            mid = low + (high-low) * ( (key-x[low]) / (x[high]-x[low]) );
            if(key==x[mid])
                return mid;
            else if(key<x[mid])
                high=mid-1;
            else
                low=mid+1;
        }
    return-1;
}