Indexed Sequential Search

Difficulty Level : Hard
Last Updated : 24 Sep, 2020

In this searching method, first of all, an index file is created, that contains some specific group or division of required record when the index is obtained, then the partial indexing takes less time cause it is located in a specified group.

Note: When the user makes a request for specific records it will find that index group first where that specific record is recorded.

Characteristics of Indexed Sequential Search:

In Indexed Sequential Search a sorted index is set aside in addition to the array.
Each element in the index points to a block of elements in the array or another expanded index.
The index is searched 1st then the array and guides the search in the array.

Note: Indexed Sequential Search actually does the indexing multiple time, like creating the index of an index.

Explanation by diagram “Indexed Sequential Search”:

Code:

C

// C program for Indexed Sequential Search
#include <stdio.h>
#include <stdlib.h>
 
void indexedSequentialSearch(int arr[], int n, int k)
{
    int elements[20], indices[20], temp, i, set = 0;
    int j = 0, ind = 0, start, end;
    for (i = 0; i < n; i += 3) {
 
        // Storing element
        elements[ind] = arr[i];
 
        // Storing the index
        indices[ind] = i;
        ind++;
    }
    if (k < elements[0]) {
        printf("Not found");
        exit(0);
    }
    else {
        for (i = 1; i <= ind; i++)
            if (k <= elements[i]) {
                start = indices[i - 1];
                end = indices[i];
                set = 1;
                break;
            }
    }
    if (set == 0) {
        start = indices[i - 1];
        end = n;
    }
    for (i = start; i <= end; i++) {
        if (k == arr[i]) {
            j = 1;
            break;
        }
    }
    if (j == 1)
        printf("Found at index %d", i);
    else
        printf("Not found");
}
 
// Driver code
void main()
{
 
    int arr[] = { 6, 7, 8, 9, 10 };
    int n = sizeof(arr) / sizeof(arr[0]);
 
    // Element to search
    int k = 8;
    indexedSequentialSearch(arr, n, k);
}

Java

// Java program for Indexed Sequential Search
 
import java.io.*;
 
class GFG {
 
    static void indexedSequentialSearch(int arr[], int n,
                                        int k)
    {
        int elements[] = new int[20];
        int indices[] = new int[20];
        int temp, i;
        int j = 0, ind = 0, start = 0, end = 0, set = 0;
        for (i = 0; i < n; i += 3) {
 
            // Storing element
            elements[ind] = arr[i];
 
            // Storing the index
            indices[ind] = i;
            ind++;
        }
        if (k < elements[0]) {
            System.out.println("Not found");
            return;
        }
        else {
            for (i = 1; i <= ind; i++)
                if (k <= elements[i]) {
                    start = indices[i - 1];
                    set = 1;
                    end = indices[i];
                    break;
                }
        }
        if (set == 0) {
            start = indices[i - 1];
            end = n;
        }
        for (i = start; i <= end; i++) {
            if (k == arr[i]) {
                j = 1;
                break;
            }
        }
        if (j == 1)
            System.out.println("Found at index " + i);
        else
            System.out.println("Not found");
    }
 
    // Driver code
 
    public static void main(String[] args)
    {
        int arr[] = { 6, 7, 8, 9, 10 };
        int n = arr.length;
 
        // Element to search
        int k = 8;
        indexedSequentialSearch(arr, n, k);
    }
}
// This code is contributed by shs..

Python3

# Python program for Indexed
# Sequential Search
 
 
def indexedSequentialSearch(arr, n, k):
 
    elements = [0] * 20
    indices = [0] * 20
    j, ind, start, end = 0, 0, 0, 0
    set_flag = 0
     
    for i in range(0, n, 3):
 
        # Storing element
        elements[ind] = arr[i]
 
        # Storing the index
        indices[ind] = i
        ind += 1
 
    if k < elements[0]:
        print("Not found")
        exit(0)
 
    else:
 
        for i in range(1, ind + 1):
            if k <= elements[i]:
                start = indices[i - 1]
                end = indices[i]
                set_flag = 1
                break
    if set_flag == 0:
        start = indices[i-1]
        end = n
    for i in range(start, end + 1):
        if k == arr[i]:
            j = 1
            break
 
    if j == 1:
        print("Found at index", i)
    else:
        print("Not found")
 
 
# Driver code
if __name__ == "__main__":
 
    arr = [6, 7, 8, 9, 10]
    n = len(arr)
 
    # Element to search
    k = 8
 
    # Function call
    indexedSequentialSearch(arr, n, k)
 
# This code is contributed by Ryuga

C#

// C# program for Indexed Sequential Search
 
using System;
 
class GFG {
     
 
 
static void indexedSequentialSearch(int []arr, int n, int k)
{
    int []elements = new int[20];
    int []indices = new int[20];
    int  i;
    int j = 0, ind = 0, start=0, end=0, set = 0;
    for (i = 0; i < n; i += 3) {
 
        // Storing element
        elements[ind] = arr[i];
 
        // Storing the index
        indices[ind] = i;
        ind++;
    }
    if (k < elements[0]) {
        Console.Write("Not found");
        return;
         
    }
    else {
        for (i = 1; i <= ind; i++)
            if (k <= elements[i]) {
                start = indices[i - 1];
                  set = 1;
                end = indices[i];
                break;
            }
    }
      if(set == 0)
    {
          start = indices[i-1];
          end = n-1;
    }
    for (i = start; i <= end; i++) {
        if (k == arr[i]) {
            j = 1;
            break;
        }
    }
    if (j == 1)
        Console.WriteLine("Found at index "+ i);
    else
        Console.WriteLine("Not found");
}
 
// Driver code
 
    public static void Main () {
        int []arr = { 6, 7, 8, 9, 10 };
        int n = arr.Length;
 
        // Element to search
        int k = 10;
        indexedSequentialSearch(arr, n, k);
    }
}
// This code is contributed by shs..

PHP

<?php
// PHP program for Indexed Sequential Search
 
function indexedSequentialSearch($arr, $n, $k)
{
    $elements = array();
    $indices = array();
    $temp = array();
    $j = 0; $ind = 0; $start=0; $end=0; $set = 0;
    for ($i = 0; $i < $n; $i += 3)
    {
 
        // Storing element
        $elements[$ind] = $arr[$i];
 
        // Storing the index
        $indices[$ind] = $i;
        $ind++;
    }
     
    if ($k < $elements[0])
    {
        echo "Not found";
 
    }
    else
    {
        for ($i = 1; $i <=$ind; $i++)
            if ($k < $elements[$i])
            {
                $start = $indices[$i - 1];
                 $set = 1;
                $end = $indices[$i];
                break;
            }
    }
      if($set == 1)
    {
          $start = $indices[$i-1];
          $end = $n;
    }
    for ($i = $start; $i <=$end; $i++)
    {
        if ($k == $arr[$i])
        {
            $j = 1;
            break;
        }
    }
    if ($j == 1)
        echo "Found at index ", $i;
    else
        echo "Not found";
}
 
// Driver code
$arr = array( 6, 7, 8, 9, 10 );
$n = count($arr);
 
// Element to search
$k = 10;
indexedSequentialSearch($arr, $n, $k);
 
// This code is contributed by shs..
?>

Output:

Found at index 2

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