Given a sorted array arr[] and a number item, the floor of the item is the greatest element smaller than or equal to item. We have to find the floor value of the given number in the sorted array using C program.

Program:

The source code to find the floor element of the given number in the sorted array is given below. The given program is compiled and executed using GCC compile on UBUNTU 18.04 OS successfully.

// C program to find floor element of given number in sorted array

#include <stdio.h>

int FindFloorItem(int arr[], int size, int item)
{
    int index = 0;

    for (index = 0; index < size - 1; index++) {
        if (arr[index] == item)
            return index;

        if (arr[index] <= item && arr[index + 1] > item)
            return index;
    }

    return -1;
}

int main()
{
    int arr[] = { 5, 7, 12, 15, 17, 19, 21 };

    int size = 0;
    int item = 8;
    int index = 0;

    size = sizeof(arr) / sizeof(arr[0]);
    index = FindFloorItem(arr, size, item);

    if (index == -1)
        printf("Floor item doesn't exist in array\n");
    else
        printf("Flooring of item %d is: %d\n", item, arr[index]);

    return 0;
}

Output:

Flooring of item 8 is: 7

Explanation:

Here, we created two functions FindFloorItem() and main() function. The FindFloorItem() function is a user-defined function, it is used to find the index of flooring item of a given number from the given sorted array.

In the main() function, we created an array arr with 7 integer elements. Then we find the flooring item of the given number item using the FindFloorItem() function from array arr and then we printed the result on the console screen.