Java: Find a specified element in a given sorted array of elements using Jump Search

Java Search: Exercise-3 with Solution

Write a Java program to find a specified element in a given sorted array of elements using Jump Search.

From Wikipedia, in computer science, a jump search or block search refers to a search algorithm for ordered lists. It works by first checking all items L_km, where ℜ ∈ ℵ and m is the block size, until an item is found that is larger than the search key. To find the exact position of the search key in the list a linear search is performed on the sublist L_{[(k-1)m, km]}.
Algorithm:
Input: An ordered list L, its length n and a search key s.
Output: The position of s in L, or nothing if s is not in L.

  a ← 0
  b ← [√n]

  while Lmin(b,n)-1 < s do
    a ← b
    b ← b + [√n]
    if a ≥ n then
      return nothing

  while La < s do
    a ← a + 1
    if a = min(b,n)
      return nothing

  if La = s then
    return a
  else
    return nothing

Sample Solution:

Java Code:

public class Main {

	public static void main(String[] args) {
        int nums[] = {1, 2, 3, 4, 5, 6, 7, 8, 21, 34, 45, 91, 120, 130, 456, 564};
        int search_num = 120;

       // Find the index of searched item
       int index_result = jumpSearch(nums, search_num);

       System.out.println(search_num + " is found at index " + index_result);

	}
	
	    public static int jumpSearch(int[] nums, int item)	    {
	        
	    	int array_size = nums.length;
	 
	        // Find block size to be jumped
	        int block_size = (int)Math.floor(Math.sqrt(array_size));
	 
	        // If the element is present find the block where element is present
	        int prev_item = 0;
	        while (nums[Math.min(block_size, array_size)-1] < item)
	        {
	            prev_item = block_size;
	            block_size += (int)Math.floor(Math.sqrt(array_size));
	            if (prev_item >= array_size)
	                return -1;
	        }
	 
	        // Using a linear search for element in block beginning with previous item
	        while (nums[prev_item] < item)
	        {
	            prev_item++;
	            if (prev_item == Math.min(block_size, array_size))
	                return -1;
	        }
	 
	        // If element is found
	        if (nums[prev_item] == item)
	            return prev_item;
	 
	        return -1;
	    } 	    
}

Sample Output:

120 is found at index 12

Flowchart:

Java Code Editor:

Contribute your code and comments through Disqus.

Previous: Write a Java program to find a specified element in a given array of elements using Linear Search.
Next: Write a Java program to find a specified element in a given array of elements using Interpolation Search.