# C++ 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.

 // C++ implementation of Shell Sort #include    /* 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

Please refer complete article on ShellSort for more details!

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