如何让我的快速排序算法按升序和降序对数组进行排序？
问题描述：
目前我的快速排序算法在情况1中按照升序对数组进行排序，但是我希望使用户选择选项2（情况2），然后按降序对数组进行排序。我必须为每种情况创建2个独立的算法吗？还是有更简单更有效的方法？如何让我的快速排序算法按升序和降序对数组进行排序？
欣赏帮助。
static void Main(string[] args)
{
Console.WriteLine("Analysis of Seismic Data.\n");
Console.WriteLine("Selection of Arrays:");
//Display all the options.
Console.WriteLine("1-Year");
Console.WriteLine("2-Month");
Console.WriteLine("3-Day");
Console.WriteLine("4-Time");
Console.WriteLine("5-Magnitude");
Console.WriteLine("6-Latitude");
Console.WriteLine("7-Longitude");
Console.WriteLine("8-Depth");
Console.WriteLine("9-Region");
Console.WriteLine("10-IRIS_ID");
Console.WriteLine("11-Timestamp\n\n");
Console.WriteLine("Use numbers to select options.");
//Read in user's decision.
Console.Write("Select which array is to be analysed:");
int userDecision = Convert.ToInt32(Console.ReadLine());
//Selected which array is to be analyzed
switch (userDecision)
{
case 1:
Console.WriteLine("\nWould you like to sort the Array in Ascending or Descending order?");
Console.WriteLine("1-Ascending");
Console.WriteLine("2-Descending");
//Create another switch statement to select either ascending or descending sort.
int userDecision2 = Convert.ToInt32(Console.ReadLine());
switch (userDecision2)
{
case 1:
//Here algorithm sorts my array in ascending order by default.
QuickSort(Years);
Console.WriteLine("Contents of the Ascending Year array: ");
foreach (var year in Years)
{
Console.WriteLine(year);
}
break;
case 2:
//How do I sort the same array in Descending order when Option 2 is selected?
//QuickSort(Years) Descendingly.
Console.WriteLine("Contents of the Descending Year array: ");
foreach (var year in Years)
{
Console.WriteLine(year);
}
break;
}
break;
case 2:
Console.WriteLine("\nWould you like to sort the Array in Ascending or Descending order?");
Console.WriteLine("1-Ascending");
Console.WriteLine("2-Descending");
//Create another switch statement to select either ascending or descending sort.
int userDecision3 = Convert.ToInt32(Console.ReadLine());
switch (userDecision3)
{
case 1:
QuickSort(Years);
Console.WriteLine("Contents of the Ascending Month array: ");
foreach (var month in Months)
{
Console.WriteLine(month);
}
break;
case 2:
//Same problem, how do I sort it in descending order?
Console.WriteLine("Contents of the Descending month array: ");
foreach (var month in Months)
{
Console.WriteLine();
}
break;
}
break;
}
}
public static void QuickSort<T>(T[] data) where T : IComparable<T>
{
Quick_Sort(data, 0, data.Length - 1);
}
public static void Quick_Sort<T>(T[] data, int left, int right) where T : IComparable<T>
{
int i, j;
T pivot, temp;
i = left;
j = right;
pivot = data[(left + right)/2];
do
{
while ((data[i].CompareTo(pivot) < 0) && (i < right)) i++;
while ((pivot.CompareTo(data[j]) < 0) && (j > left)) j--;
if (i <= j)
{
temp = data[i];
data[i] = data[j];
data[j] = temp;
i++;
j--;
}
} while (i <= j);
if (left < j) Quick_Sort(data, left, j);
if (i < right) Quick_Sort(data, i, right);
}
答
你可以改变你快速排序的方法来接受IComparer<T> comparer，和然后用它来进行比较。
然后，如果您需要默认比较订单，则可以使用Comparer<T>.Default，或者您可以使用Comparer<T>.Create()来创建自定义（例如反转）比较。
可编译例子：
using System;
using System.Collections.Generic;
namespace ConsoleApp1
{
class Program
{
static void Main()
{
int[] data = {6, 7, 2, 3, 8, 1, 9, 0, 5, 4};
QuickSort(data);
Console.WriteLine(string.Join(", ", data)); // Prints 0, 1, 2, 3, 4, 5, 6, 7, 8, 9
QuickSort(data, Comparer<int>.Create((a, b) => b.CompareTo(a)));
Console.WriteLine(string.Join(", ", data)); // Prints 9, 8, 7, 6, 5, 4, 3, 2, 1, 0
}
public static void QuickSort<T>(T[] data)
{
Quick_Sort(data, 0, data.Length - 1, Comparer<T>.Default);
}
public static void QuickSort<T>(T[] data, IComparer<T> comparer)
{
Quick_Sort(data, 0, data.Length - 1, comparer);
}
public static void Quick_Sort<T>(T[] data, int left, int right, IComparer<T> comparer)
{
int i, j;
T pivot, temp;
i = left;
j = right;
pivot = data[(left + right)/2];
do
{
while ((comparer.Compare(data[i], pivot) < 0) && (i < right)) i++;
while ((comparer.Compare(pivot, data[j]) < 0) && (j > left)) j--;
if (i <= j)
{
temp = data[i];
data[i] = data[j];
data[j] = temp;
i++;
j--;
}
} while (i <= j);
if (left < j) Quick_Sort(data, left, j, comparer);
if (i < right) Quick_Sort(data, i, right, comparer);
}
}
}
这有两个好处：
- 类型
T并不需要实现IComparable<T>。您可以传入进行比较的IComparer<T>对象。 - 您可以通过传递不同的自定义
IComparer<T>对象以多种方式对相同的数据进行排序。
这是由一些LINQ的IEnumerable的扩展所采用的方法，例如Enumerable.OrderBy()
+0
感谢您的解决方案。我是编程新手，还没有学习过接口。我应该研究什么才能更好地理解您在此处展示的具体解决方案？此解决方案也使用任何内置的排序和搜索功能，因为我不允许在我的任务中使用这些功能。 – Ulfren
+0
@IllimarIssak它没有使用任何内置的排序或搜索;它只是使用一个接口来指定与元素进行比较的方式。欲了解更多信息，请参阅['IComparer
答
添加参数，允许改变比较的结果
(data[i].CompareTo(pivot) < 0)
and
(pivot.CompareTo(data[j]) < 0)
一个简单的方法：参数descending +1/-1和使用
data[i].CompareTo(pivot) * descending < 0
答
只是平添几分奶油对@Matthew沃森回答。在阅读@Illimar的文章后，他想让用户选择以升序模式还是降序模式对数组进行排序。我刚才编辑@Matthew工作拿出了以下内容：
using System;
using System.Collections.Generic;
using System.Threading;
namespace Test1
{
class Program
{
static void Main(string[] args)
{
MySorter();
}
static void MySorter()
{
int[] data = MyArray();
Console.WriteLine();
Console.WriteLine("Chose 1 to sort Ascending or 2 to sort Descending:");
//int choice = Console.Read();
ConsoleKeyInfo choice = Console.ReadKey();
Console.WriteLine();
if (choice.Key == ConsoleKey.D1 || choice.Key == ConsoleKey.NumPad1)
{
QuickSort(data);
string result = string.Join(", ", data);
Console.WriteLine(result);
Thread.Sleep(4000);
}
else if (choice.Key == ConsoleKey.D2 || choice.Key == ConsoleKey.NumPad2)
{
QuickSort(data, Comparer<int>.Create((a, b) => b.CompareTo(a)));
Console.WriteLine(string.Join(", ", data));
Thread.Sleep(4000);
}
else
{
Console.WriteLine("wrong input.");
Thread.Sleep(2000);
Environment.Exit(0);
}
}
public static int[] MyArray()
{
Console.WriteLine("Enter a total of 10 numbers to be sorted: ");
int[] InputData = new int[10];
for (int i = 0; i < InputData.Length; i++)
{
var pressedkey = Console.ReadKey();
int number;
bool result = int.TryParse(pressedkey.KeyChar.ToString(), out number);
if (result)
{
InputData[i] = number;
}
}
return InputData;
}
public static void QuickSort<T>(T[] data)
{
Quick_Sort(data, 0, data.Length - 1, Comparer<T>.Default);
}
public static void QuickSort<T>(T[] data, IComparer<T> comparer)
{
Quick_Sort(data, 0, data.Length - 1, comparer);
}
public static void Quick_Sort<T>(T[] data, int left, int right, IComparer<T> comparer)
{
int i, j;
T pivot, temp;
i = left;
j = right;
pivot = data[(left + right)/2];
do
{
while ((comparer.Compare(data[i], pivot) < 0) && (i < right)) i++;
while ((comparer.Compare(pivot, data[j]) < 0) && (j > left)) j--;
if (i <= j)
{
temp = data[i];
data[i] = data[j];
data[j] = temp;
i++;
j--;
}
} while (i <= j);
if (left < j) Quick_Sort(data, left, j, comparer);
if (i < right) Quick_Sort(data, i, right, comparer);
}
}
}
所以在用户上面给出要分类为输入数字，然后选择如何排序应该怎么办？
您也可以传递决定排序顺序的参数器，但例如，在Linq，微软的开发人员决定创建一个自己的方法'OrderByDescending（）' – fubo
我不允许使用内置的排序方法 – Ulfren