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Java Program for ShellSort

In shellSort, we make the array h-sorted for a large value of h. We keep reducing the value of h until it becomes 1. An array is said to be h-sorted if all sublists of every h’th element is sorted. 




// Java implementation of ShellSort
class ShellSort {
 /* An utility function to print array of size n*/
 static void printArray(int arr[])
 {
  int n = arr.length;
  for (int i = 0; i < n; ++i)
   System.out.print(arr[i] + " ");
  System.out.println();
 }
 
 /* function to sort arr using shellSort */
 int sort(int arr[])
 {
  int n = arr.length;
 
  // Start with a big gap, then reduce the gap
  for (int gap = n / 2; gap > 0; gap /= 2) {
   // Do a gapped insertion sort for this gap size.
   // The first gap elements a[0..gap-1] are already
   // in gapped order keep adding one more element
   // until the entire array is gap sorted
   for (int i = gap; i < n; i += 1) {
    // add a[i] to the elements that have been gap
    // sorted save a[i] in temp and make a hole at
    // position i
    int temp = arr[i];
 
    // shift earlier gap-sorted elements up until
    // the correct location for a[i] is found
    int j;
    for (j = i; j >= gap && arr[j - gap] > temp; j -= gap)
     arr[j] = arr[j - gap];
 
    // put temp (the original a[i]) in its correct
    // location
    arr[j] = temp;
   }
  }
  return 0;
 }
 
 // Driver method
 public static void main(String args[])
 {
  int arr[] = { 12, 34, 54, 2, 3 };
  System.out.println("Array before sorting");
  printArray(arr);
 
  ShellSort ob = new ShellSort();
  ob.sort(arr);
 
  System.out.println("Array after sorting");
  printArray(arr);
 }
}
/*This code is contributed by Rajat Mishra */

Output:
Array before sorting
12 34 54 2 3 
Array after sorting
2 3 12 34 54

Time Complexity: O(n2)
Auxiliary Space: O(1)

Please refer complete article on ShellSort for more details!


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