冒泡排序中的 Java 交换和比较

Question

public class SortingArray
{
   public static void main(String[] args)
   {
      int[] array1 = { 1, 2, 3, 4, 5};
      bubbleSort(array1);
   }

   public static void bubbleSort(int[] array2)
   {      
      // Display the array's contents.
      System.out.println("Original order: ");
      for (int element : array2)
         System.out.print(element + " ");

      int lastPos;     // Position of last element to compare
      int index;       // Index of an element to compare
      int temp;        // Used to swap to elements
        int count = 0;
      int count2 = 1;

      // The outer loop positions lastPos at the last element
      // to compare during each pass through the array. Initially
      // lastPos is the index of the last element in the array.
      // During each iteration, it is decreased by one.
      for (lastPos = array2.length - 1; lastPos >= 0; lastPos--)
      {
         // The inner loop steps through the array, comparing
         // each element with its neighbor. All of the elements
         // from index 0 thrugh lastPos are involved in the
         // comparison. If two elements are out of order, they
         // are swapped.
         for (index = 0; index <= lastPos - 1; index++)
         {
            count2++;
            // Compare an element with its neighbor.
            if (array2[index] > array2[index + 1])
            {
                    count++;
               // Swap the two elements.
               temp = array2[index];
               array2[index] = array2[index + 1];
               array2[index + 1] = temp;
            }
         }
      }
      count2++;

      // Display the array's contents.
      System.out.println("\nSorted order: ");
      for (int element : array2)
         System.out.print(element + " ");

      System.out.print("\n Swaps:" + count);
      System.out.print("\n Comparisons:" + count2);


   }

}

我正在尝试在一个简单的冒泡排序程序中计算比较和交换，并且我知道我计算了正确数量的交换（在本例中为 0），但我不知道如何跟踪比较.我必须使用这个特定的代码，只需稍作修改。有人可以帮助我了解使用这个硬编码的 int 数组将进行多少次比较。现在，当我运行程序时，我得到 12，我认为这是正确的，但我并不是 100% 肯定。

Answer 1

编辑：原始代码确实正确实现了冒泡排序。

所以，请保留您的原始代码，只需使用下面的代码作为参考，以获取正确的比较计数。

无论如何，仅供参考，这里是另一个常见的实现，具有正确的交换和比较计数：

public class SortingArray
{
   public static void main(String[] args)
   {
      int[] array1 = { 5, 4, 3, 2, 1};
      bubbleSort(array1);
   }

   public static void bubbleSort(int[] array2)
   {      
      // Display the array's contents.
      System.out.println("Original order: ");
      for (int element : array2)
         System.out.print(element + " ");

      //int lastPos;     // Position of last element to compare
      int index;       // Index of an element to compare
      int temp;        // Used to swap to elements
      int count = 0;
      int count2 = 0;
      boolean swapped = true;


      while (swapped == true)
      {
         swapped = false;
         // The inner loop steps through the array, comparing
         // each element with its neighbor. All of the elements
         // from index 0 thrugh lastPos are involved in the
         // comparison. If two elements are out of order, they
         // are swapped.
         for (index = 0; index < array2.length - 1; index++)
         {
            count2++;
            // Compare an element with its neighbor.
            if (array2[index] > array2[index + 1])
            {
               count++;
               // Swap the two elements.
               temp = array2[index];
               array2[index] = array2[index + 1];
               array2[index + 1] = temp;
               swapped = true;
            }

         }
      }
      //count2++;

      // Display the array's contents.
      System.out.println("\nSorted order: ");
      for (int element : array2)
         System.out.print(element + " ");

      System.out.print("\n Swaps:" + count);
      System.out.print("\n Comparisons:" + count2);


   }

}

输出：

Original order: 
5 4 3 2 1 
Sorted order: 
1 2 3 4 5 
 Swaps:10
 Comparisons:20

对于您的排序示例：

int[] array1 = { 1, 2, 3, 4, 5};

输出：

Original order: 
1 2 3 4 5 
Sorted order: 
1 2 3 4 5 
 Swaps:0
 Comparisons:4