目前，我的快速排序算法在第1种情况下按升序排序数组，但我想这样做，以便当用户选择选项2（情况2）时，它会按降序对数组进行排序。我是否必须为每种情况创建2个独立的算法？或者有更简单，更有效的方法吗？
感谢帮助。
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);
}
答案 0 :(得分：2)
您可以将Quicksort方法更改为接受IComparer<T> comparer，然后使用它进行比较。
如果您需要默认比较顺序，则可以使用Comparer<T>.Default，或者可以使用Comparer<T>.Create()创建自定义（例如反转）比较。
可编辑的例子：
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：
T不需要实现IComparable<T>。您可以传入进行比较的IComparer<T>对象。IComparer<T>对象，以多种方式对相同的数据进行排序。这是许多Linq IEnumerable扩展所采用的方法，例如Enumerable.OrderBy()
答案 1 :(得分：0)
添加允许更改比较结果的参数
(data[i].CompareTo(pivot) < 0)
and
(pivot.CompareTo(data[j]) < 0)
一种简单的方法：参数descending +1/-1并使用
data[i].CompareTo(pivot) * descending < 0
答案 2 :(得分：0)
在@Matthew Watson的回答中加入一点奶油。在阅读@Illimar的帖子后，他想让用户选择以升序模式或降序模式对数组进行排序。我刚刚编辑了@Matthew的工作来提出以下内容：
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);
}
}
}
所以在上面用户给出了要作为输入排序的数字，然后选择如何进行排序？