ShellSort is mainly a variation of Insertion Sort. In insertion sort, we move elements only one position ahead. When an element has to be moved far ahead, many movements are involved. The idea of shellSort is to allow exchange of far items. 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.
Following is the implementation of ShellSort.
Array before sorting: 12 34 54 2 3 Array after sorting: 2 3 12 34 54
Time Complexity: Time complexity of above implementation of shellsort is O(n2). In the above implementation gap is reduce by half in every iteration. There are many other ways to reduce gap which lead to better time complexity. See this for more details.
Other Sorting Algorithms on GeeksforGeeks/GeeksQuiz:
- Selection Sort
- Bubble Sort
- Insertion Sort
- Merge Sort
- Heap Sort
- Radix Sort
- Counting Sort
- Bucket Sort
- C++ Program for ShellSort
- Java Program for ShellSort
- Farthest index that can be reached from the Kth index of given array by given operations
- Split array into equal length subsets with maximum sum of Kth largest element of each subset
- Minimize difference between maximum and minimum array elements by exactly K removals
- Count subsequences for every array element in which they are the maximum
- Find the order of execution of given N processes in Round Robin Scheduling
- Check if a given string can be converted to another by given possible swaps
- Sort given array to descending-lowest-ascending form
- Maximize cost to empty given array by repetitively removing K array elements
- Sorting strings from the text file
- Print all numbers up to N in words in lexicographical order
- Minimize cost to convert all array elements to 0
- Reduce array to longest sorted array possible by removing either half of given array in each operation
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