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C++ Program for ShellSort

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  • Last Updated : 10 Jun, 2022
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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. 

CPP




// C++ implementation of Shell Sort
#include <iostream>
 
/* function to sort arr using shellSort */
void shellSort(int arr[], int n)
{
 // 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 arr[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 arr[i] to the elements that have been gap sorted
   // save arr[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 arr[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 arr[i]) in its correct location
   arr[j] = temp;
  }
 }
}
 
void printArray(int arr[], int n)
{
 for (int i = 0; i < n; i++)
  std::cout << arr[i] << " ";
 std::cout << "\n";
}
 
int main()
{
 int arr[] = { 12, 34, 54, 2, 3 };
 int n = sizeof(arr) / sizeof(arr[0]);
 
 std::cout << "Array before sorting: \n";
 printArray(arr, n);
 
 shellSort(arr, n);
 
 std::cout << "Array after sorting: \n";
 printArray(arr, n);
}


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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