如何在没有排序 function 的情况下使用给定顺序对 C# 中的数组元素进行排序？

Question

I've been searching about an algorithm that sorts "strings" with a given order.

Input : [W, R, B, G, G, R, W, B] ( obviously, just random )

Output : [R, R, W, W, B, B, G, G]

I want to do like a " Two-Pass Algorithm ".

Something like:

using System;
using System.Collections.Generic;
using System.Drawing;

namespace ConsoleApp5
{
    class Program2
    {
        static void Main(string[] args)
        {
            List<Color> colors = new List<Color>() { Color.White, Color.Red, Color.Green, Color.Blue }; // Random Ordered Array
            int j = 0;
            int k = colors.Count;
            int i = 0;
            while (j < k)
            {
                if (colors[j] == Color.White)
                {
                    j += 1;
                }
                else if (colors[j] == Color.Blue)
                {
                    swap(colors[j], colors[--k]);
                    Console.WriteLine(colors[j]);
                }
                else
                {
                    swap(colors[j++], colors[i++]);
                }
                i += 1;
            }

            void swap(Color a, Color b)
            {
                Color temp = a;
                a = b;
                b = temp;

            }
        }
    }
}

EDIT 1

I was able to print "RRWWGG" from this code:

using System;
using System.Collections.Generic;
using System.Drawing;

namespace ConsoleApp5
{
    class Program2
    {
        static void Main(string[] args)
        {
            List<String> colors = new List<String>() { "W", "R", "G", "W", "R", "G"}; // Random Ordered Array
            int start = 0;
            int end = colors.Count - 1;
            int current = 0;

            while (current <= end && start < end)
            {
                if(colors[current] == "R")
                {
                    swap(colors, current, start);
                    start++;
                    current++;
                }
                else if (colors[current] == "G")
                {
                    swap(colors, current, end);
                    end--;
                }
                else
                {
                    current++;
                }

            }
            for(int i = 0; i < colors.Count; i++)
            {
                Console.WriteLine(i+colors[i]);
            }
        }
        static void swap(List<String> colors, int a, int b)
        {
            String temp = colors[a];
            colors[a] = colors[b];
            colors[b] = temp;

        }
    }
}

Now, I want to do the same algorithm to place W and B in the middle, given that R must be placed on the left and G on the right.

I added B to the array with this code:

using System;
using System.Collections.Generic;
using System.Drawing;

namespace ConsoleApp5
{
    class Program2
    {
        static void Main(string[] args)
        {
            List<String> colors = new List<String>() { "W", "R", "G", "W", "R", "G", "B", "B" }; // Random Ordered Array
            int start = 0;
            int end = colors.Count - 1;
            int current = 0;

            while (current <= end && start < end)
            {
                if(colors[current] == "R")
                {
                    swap(colors, current, start);
                    start++;
                    current++;
                }
                else if (colors[current] == "G")
                {
                    swap(colors, current, end);
                    end--;
                }
                else
                {
                    current++;
                }

            }
            for(int i = 0; i < colors.Count; i++)
            {
                Console.WriteLine(i+colors[i]);
            }
        }
        static void swap(List<String> colors, int a, int b)
        {
            String temp = colors[a];
            colors[a] = colors[b];
            colors[b] = temp;

        }
    }
}

The result of the above code was: [R, R, B, W, W, B, G, G] .

I want the result to be [R, R, W, W, B, B, G, G] without " library's sort function " and only with this kind of algorithm.

Answer 1

A typical approach would be to create a mapping between your letters and something that sorts according to your specifications. For example

var sortorder = new Dictionary<char, int>(){
{'R', 0},
{'W', 1},
{'B', 2},
{'G', 3}};
var input = new []{'W', 'R', 'B', 'G', 'G', 'R', 'W', 'B'];
var sorted = input.OrderBy(i => sortorder[i]);

If you want to sort full strings instead of just characters you could instead create char->char mappings and replace all the characters in the strings before sorting.