Insertion Sort

Insertion sort is a simple sorting algorithm and it picks
one item at a time, sort the elements finally produce the sorted array.
Insertion sort is good for small size elements but not for large elements.

Insertion sort iterates though out the array and iterates
are equal to array size. Each iteration, insertion sort removes one element
from the input data and finds the location it belongs within the sorted list,
and inserts it there. It repeats the same until end of the input array.  Sorting typically done in place by comparing
the each element and at every position and check there is any value largest against
it.  If larger element found it leaves
the element in place and moves to the next and incase of smaller it finds the
correct position within the sorted list, and place it there. 

However, advantages of Insertion Sort are that it is
efficient for (quite) small data sets, adaptive for data sets that are already
substantially sorted, stable (i.e. does not change the relative order of
elements with equal keys), In-place ( i.e. only requires a constant amount O(1)
of additional memory space) and online (i.e. can sort a list as it receives
it).

Insertion Sort example

Worst Case Performance: 
O(n²) comparisons

Best Case Performance: O(n) comparisons

Average Case Performance: O(n²)
comparisons

Worst Case space complexity: O(n) total
and O(1) auxiliary

Algorithm for Insertion Sort:

// Sort an arr[] of size n

insertionSort(arr, n)

Loop from i = 1 to n-1.

……a) Pick element arr[i] and insert it into sorted sequence arr[0…i-1]

Pseudo code for Insertion Sort:

for
i ← 1 to length(A)

    j ← i

    while j > 0 and A[j-1] > A[j]

        swap A[j] and A[j-1]

        j ← j - 1

    end while

end
for

Let us see the below example for Insertion sort:

2, 4, 9, 6, 23, 12, 34, 0, 1,

2, 4, 9, 6, 23, 12, 34, 0, 1,

2, 4, 6, 9, 23, 12, 34, 0, 1,

2, 4, 6, 9, 23, 12, 34, 0, 1,

2, 4, 6, 9, 12, 23, 34, 0, 1,

2, 4, 6, 9, 12, 23, 34, 0, 1,

0, 2, 4, 6, 9, 12, 23, 34, 1,

0, 1, 2, 4, 6, 9, 12, 23, 34,

 

Program for Insertion Sort in  Java:

import java.util.Scanner;
public class InsertionSort
{
    public static void sort( int arr[] )
    {
        int size = arr.length;
        int i, j, temp;
        for (i = 1; i< size; i++)
        {
            j = i;
            temp = arr[i];   
            while (j > 0 && temp < arr[j-1])
            {
               arr[j] = arr[j-1];
                j = j-1;
            }
            arr[j] = temp;           
        }       
    }   
    public static void main(String[] args)
    {
        Scanner input = new Scanner( System.in );       
        System.out.println("Insertion Sort over the given input\n");
        int n, i;
        /* Accept a number for sorting elements */
        System.out.println("Enter size of integer elements");
        n = input.nextInt();
        /* Create integer array on n elements */
        int arr[] = new int[ n ];
        /* Accept elements */
        System.out.println("\nEnter "+ n +" integer elements");
        for (i = 0; i < n; i++)
            arr[i] = input.nextInt();
       /* Call method sort */
        sort(arr);
        /* Print sorted Array */
        System.out.println("\nElements after sorting ");       
        for (i = 0; i < n; i++)
        System.out.print(arr[i]+" ");           
        System.out.println();                    
    }   
}

Output is :

3, 12, 34, 0, 1,

2, 4, 9, 6, 23, 12, 34, 0, 1,

2, 4, 6, 9, 23, 12, 34, 0, 1,

2, 4, 6, 9, 23, 12, 34, 0, 1,

2, 4, 6, 9, 12, 23, 34, 0, 1,

2, 4, 6, 9, 12, 23, 34, 0, 1,

0, 2, 4, 6, 9, 12, 23, 34, 1,

0, 1, 2, 4, 6, 9, 12, 23, 34, - See more at:
http://www.java2novice.com/java-interview-programs/insertion-sort/#sthash.KEc6oyNn.dpuf

2,
4, 9, 6, 23, 12, 34, 0, 1,

2, 4, 9, 6, 23, 12, 34, 0, 1,

2, 4, 6, 9, 23, 12, 34, 0, 1,

2, 4, 6, 9, 23, 12, 34, 0, 1,

2, 4, 6, 9, 12, 23, 34, 0, 1,

2, 4, 6, 9, 12, 23, 34, 0, 1,

0, 2, 4, 6, 9, 12, 23, 34, 1,

0, 1, 2, 4, 6, 9, 12, 23, 34, - See more at:
http://www.java2novice.com/java-interview-programs/insertion-sort/#sthash.KEc6oyNn.dpuf