java - 如何在Java中的快速排序中计算比较和交换？

Question

我有一个简单的方法来使用快速排序对 int 数组进行排序。我不知道如何正确计算交换和比较的次数，因为该算法是递归的:

public void quicksort(int tablica[], int x, int y) {
    int i,j,v,temp;
    i=x;
    j=y;
    int swaps=0;
    int comparisons=0;
    v=tablica[(x+y) / 2];
    while (i<=j)
    {
        while (tablica [i] <v)
        {
            i++;
        }
        while (tablica [j] >v)
        {
            j--;
        }
        if (i<=j){
            temp = tablica [i];
            tablica [i]=tablica[j];
            tablica [j] = temp;
            i++;
            j--;
            swaps++;
        }
        comparisons++;
    }
    if (x<j)
        quicksort(tablica,x,j);
    if (i<y)
        quicksort(tablica,i,y);
    System.out.println("Comparisons: " + comparisons);
    System.out.println("Swaps: " + swaps);
}

使用小(10 个整数)数组运行它会返回:

Comparisons: 1
Swaps: 1
Comparisons: 1
Swaps: 1
Comparisons: 2
Swaps: 2
Comparisons: 1
Swaps: 1
Comparisons: 1
Swaps: 1
Comparisons: 1
Swaps: 1
Comparisons: 2
Swaps: 1
Comparisons: 4
Swaps: 4

如何正确地做到这一点？

Answer 1

定义一个类变量，并在每次运行快速排序方法时更新类变量。

示例

public class example {
  private int swaps=0;
  private int comparisons=0;

  public void quicksort(int tablica[], int x, int y) {
    int i,j,v,temp;
    i=x;
    j=y;

    v=tablica[(x+y) / 2];
    while (i<=j)
    {
        while (tablica [i] <v)
        {
            i++;
        }
        while (tablica [j] >v)
        {
            j--;
        }
        if (i<=j){
            temp = tablica [i];
            tablica [i]=tablica[j];
            tablica [j] = temp;
            i++;
            j--;
            swaps++;
        }
        comparisons++;
    }
    if (x<j)
        quicksort(tablica,x,j);
    if (i<y)
        quicksort(tablica,i,y);
    System.out.println("Comparisons: " + comparisons);
    System.out.println("Swaps: " + swaps);
  }
}