Java Data Structure How to - Implement a Shell sort

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Question

We would like to know how to implement a Shell sort.

Answer

public class MainClass {
  public static void main(String[] args) {
    int[] intArray = { 1, 9, 2, 8, 3, 7, 4, 6, 5 };
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    for (int i : intArray) {
      System.out.println(i);
    }

    shellSort(intArray);
    System.out.println("after: ");
    for (int i : intArray) {
      System.out.println(i);
    }
  }

  public static void shellSort(int[] intArray) {
    int inner, outer;
    int temp;

    int h = 1;
    while (h <= intArray.length / 3){
      h = h * 3 + 1;
    }
    while (h > 0) {
      for (outer = h; outer < intArray.length; outer++) {
        temp = intArray[outer];
        inner = outer;

        while (inner > h - 1 && intArray[inner - h] >= temp) {
          intArray[inner] = intArray[inner - h];
          inner -= h;
        }
        intArray[inner] = temp;
      }
      h = (h - 1) / 3;
    }
  }
}   

The code above generates the following result.

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