我找到了以下代码。我试图了解哪种排序方法最快，哪些排序方法使用最多和最少的比较。任何人都知道如何在这里添加一些代码来做到这一点？我想计算每种比较的总数。
//***********************************************************************************
// Sorting.java
//
// Contains various sort algorithms that operate on an array of comparable objects.
//
//************************************************************************************
public class Sorting
{
//------------------------------------------------------------------------------------
// Sorts the specified array of integers using the selection sort algorithm.
//------------------------------------------------------------------------------------
public static void selectionSort (Comparable[] data)
{
int min;
for (int index = 0; index < data.length-1; index ++)
{
min = index;
for (int scan = index+1; scan < data.length; scan++)
if (data[scan].compareTo(data[min]) < 0)
min = scan;
swap (data, min, index);
}
}
//---------------------------------------------------------------------------------------
// Swaps to elements in the specified array.
//---------------------------------------------------------------------------------------
private static void swap (Comparable[] data, int index1, int index2)
{
Comparable temp = data[index1];
data[index1] = data[index2];
data[index2] = temp;
}
//---------------------------------------------------------------------------------------
// Sorts the specified array of objects using an insertion sort algorithm.
//---------------------------------------------------------------------------------------
public static void insertionSort (Comparable[] data)
{
for (int index = 1; index < data.length; index++)
{
Comparable key = data[index];
int position = index;
// shift larger values to the right
while (position > 0 && data[position-1].compareTo(key) > 0)
{
data[position] = data[position-1];
position--;
}
data[position] = key;
}
}
//---------------------------------------------------------------------------------------
// Sorts the specified array of objects using a bubble sort algorithm.
//---------------------------------------------------------------------------------------
public static void bubbleSort (Comparable[] data)
{
int position, scan;
for (position = data.length - 1; position >= 0; position--)
{
for (scan = 0; scan <= position - 1; scan ++)
if (data[scan].compareTo(data[scan+1]) >0)
swap (data, scan, scan+1);
}
}
//---------------------------------------------------------------------------------------
// Sorts the specified array of objects using the quick sort algorithm.
//---------------------------------------------------------------------------------------
public static void quickSort (Comparable[] data, int min, int max)
{
int pivot;
if (min < max)
{
pivot = partition (data, min, max); // make partitions
quickSort(data, min, pivot-1); //sort left paritions
quickSort(data, pivot+1, max); //sort right paritions
}
}
//---------------------------------------------------------------------------------------
// Creates the partitions needed for quick sort.
//---------------------------------------------------------------------------------------
public static int partition (Comparable[] data, int min, int max)
{
//Use first element as the partition value
Comparable partitionValue = data[min];
int left = min;
int right = max;
while (left < right)
{
// Search for an element that is greater than the partition element
while (data[left].compareTo(partitionValue) <= 0 && left < right)
left++;
// Search for an element that is less than the partition element
while (data[right].compareTo(partitionValue) > 0)
right--;
if (left < right)
swap (data, left, right);
}
// Move the partition element to its final position
swap (data, min, right);
return right;
}
//---------------------------------------------------------------------------------------
// Sorts the specified array of objects using the merge sort algorithm.
//---------------------------------------------------------------------------------------
public static void mergeSort (Comparable[] data, int min, int max)
{
if (min < max)
{
int mid = (min + max) / 2;
mergeSort(data, min, mid);
mergeSort(data, mid+1, max);
merge (data, min, mid, max);
}
}
//---------------------------------------------------------------------------------------
// Sorts the specified array of objects using the merge sort algorithm.
//---------------------------------------------------------------------------------------
public static void merge (Comparable[] data, int first, int mid, int last)
{
Comparable[] temp = new Comparable[data.length];
int first1 = first, last1 = mid; //endpoints of first subarray
int first2 = mid + 1, last2 = last; //endpoints of second subarray
int index = first1; // next index open in temp array
// Copy smaller item from each subarry into temp until one of the subarrays is exhausted
while (first1 <= last1 && first2 <= last2)
{
if (data[first1].compareTo(data[first2]) < 0)
{
temp[index] = data[first1];
first1++;
}
else
{
temp[index] = data[first2];
first2++;
}
index++;
}
// Copy remaining elements from first subarray, if any
while (first1 <= last1)
{
temp[index] = data[first1];
first1++;
index++;
}
// Copy remaining elements from second subarray, if any
while (first2 <= last2)
{
temp[index] = data[first2];
first2++;
index++;
}
// Copy merged data into original array
for (index = first; index <= last; index++)
data[index] = temp[index];
}
}
答案 0 :(得分：5)
如果您对速度感兴趣，请使用Arrays.sort()。如果你在学术上对各种排序技术的内容感兴趣，那么look at Wikipedia可能会更快。如果你想让我们为你做功课......我们不会，抱歉。
编辑：我想这对我来说是公平的：有没有理由你不能在每个方法的开头将一个整数初始化为0，每当有趣的事情发生时就增加它，然后在结束？
答案 1 :(得分：1)
答案 2 :(得分：1)
您应该定义一个实现计数的抽象类，然后定义一些实现算法的派生类。主程序看起来像这样：
List<String> list = new ArrayList<String>();
// TODO: add some elements to the list
SortingAlgorithm alg = new BubbleSort();
alg.sort(list);
alg.printSummary();
现在实现计数的抽象类：
public abstract class SortingAlgorithm<T> {
/* the actual algorithm, which uses the compare and swap methods. */
public abstract void sort(List<T> list);
private long compares = 0;
private long swaps = 0;
protected int compare(T a, T b) {
compares++;
return a.compareTo(b);
}
protected void swap(int index1, int index2) {
swaps++;
// TODO: do the actual swapping
}
public void printSummary() {
// TODO
}
}
具体算法现在只需要实现sort方法。如何做到这一点留给读者练习。