package Sorts;

/**
 * @author dpunosevac
 */
public class ShellSort {

  /**
   * This method implements Generic Shell Sort.
   * @param array The array to be sorted
   */
  public static void shellSort(Comparable[] array) {
    int N = array.length;
    int h = 1;

    while (h < N/3) {
      h = 3 * h + 1;
    }

    while (h >= 1) {
      for (int i = h; i < N; i++) {
        for (int j = i; j >= h && less(array[j], array[j-h]); j -= h) {
          exch(array, j, j - h);
        }
      }

      h /= 3;
    }
  }

  /**
   * Helper method for exchanging places in array
   * @param array The array which elements we want to swap
   * @param i index of the first element
   * @param j index of the second element
   */
  private static void exch(Comparable[] array, int i, int j) {
    Comparable swap = array[i];
    array[i] = array[j];
    array[j] = swap;
  }

  /**
   * This method checks if first element is less then the other element
   * @param v first element
   * @param w second element
   * @return true if the first element is less then the second element
   */
  private static boolean less(Comparable v, Comparable w) {
    return v.compareTo(w) < 0;
  }

  public static void main(String[] args) {
    // Integer Input
    int[] arr1 = {4,23,6,78,1,54,231,9,12};
    Integer[] array = new Integer[arr1.length];

    for (int i=0;i<arr1.length;i++) {
      array[i] = arr1[i];
    }

    shellSort(array);

    for (int i = 0; i < array.length; i++) {
      System.out.println(array[i]);
    }
  }
}