ShellSort.java

package algorithms.sort;

/**
 * UnStable sort
 * time: O(n^2) Quadratic Time(could be better depending on the Gap)
 * in-place Algorithm
 */
public class ShellSort {

    public static int[] shellSort(int[] arr) {
        for (int gap = arr.length / 2; gap > 0; gap /= 2) {

            for (int i = gap; i < arr.length; i++) {
                int newElement = arr[i];

                int j;
                for (j = i; j >= gap && arr[j - gap] > newElement; j -= gap) {
                    arr[j] = arr[j - gap];
                }
                arr[j] = newElement;
            }
        }

        return arr;
    }

    public static void main(String[] args) {

        int[] arr = {23, 435, 5, 6, 88, 99, -32, 4, -665};
        int[] sortedArray = shellSort(arr);

        for (int item : sortedArray) {
            System.out.println(item);
        }
    }
}