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!