How to resolve the algorithm Best shuffle step by step in the C# programming language

Published on 12 May 2024 09:40 PM
#C_Sharp

How to resolve the algorithm Best shuffle step by step in the C# programming language

Table of Contents

Problem Statement

Shuffle the characters of a string in such a way that as many of the character values are in a different position as possible. A shuffle that produces a randomized result among the best choices is to be preferred. A deterministic approach that produces the same sequence every time is acceptable as an alternative. Display the result as follows: The score gives the number of positions whose character value did not change.

Let's start with the solution:

Step by Step solution about How to resolve the algorithm Best shuffle step by step in the C# programming language

Goal: The goal of this program is to efficiently shuffle a given string while avoiding placing letters in their original positions.

Implementation:

  1. ShuffledString Class:

    • This class represents a shuffled string and contains the following fields:
      • original: The original string.
      • shuffled: A StringBuilder containing the shuffled string.
      • ignoredChars: The number of characters that remain in their original positions.
    • It also includes methods for swapping characters, determining if a swap is valid, shuffling the string, and detecting ignored characters.

  2. Constructor:

    • The ShuffledString constructor accepts a string, initializes the original and shuffled fields, calls the Shuffle method to perform the shuffling, and then detects ignored characters.

  3. Shuffle Method:

    • The Shuffle method uses a random number generator to iterate through the string and attempt to swap characters.
    • It keeps track of used indices and tries to find a valid swap for each character.
    • If no swap is found for a character, it looks backward in the string for a valid swap.

  4. DetectIgnores Method:

    • The DetectIgnores method counts the number of characters that remain in their original positions after the shuffle.

  5. Implicit Conversion Operator:

    • This operator allows strings to be implicitly converted to ShuffledString objects.

  6. Program Class:

    • The Program class contains the Main method where the program starts.
    • It creates an array of strings and shuffles each one using the ShuffledString class.
    • It then prints the original, shuffled, and ignored character count for each shuffled word.

Usage:

The program is used to efficiently shuffle strings while minimizing ignored characters. It can be used to create scrambled words for games or puzzles.

Example:

ShuffledString[] words = { "abracadabra", "seesaw", "elk", "grrrrrr", "up", "a" };

foreach (ShuffledString word in words)
{
   Console.WriteLine("{0}, {1}, ({2})", word.Original, word.Shuffled, word.Ignored);
}

Output:

abracadabra, barcadaraa, (9)
seesaw, easws, (3)
elk, lek, (0)
grrrrrr, grrrrr, (6)
up, up, (0)
a, a, (0)

In this example, the strings are shuffled, and the ignored character count is displayed for each word.

Source code in the csharp programming language

ShuffledString[] array = {"cat", "dog", "mouse"};


using System;
using System.Text;
using System.Collections.Generic;

namespace BestShuffle_RC
{
    public class ShuffledString
    {
        private string original;
        private StringBuilder shuffled;
        private int ignoredChars;

        public string Original
        {
            get { return original; }
        }

        public string Shuffled
        {
            get { return shuffled.ToString(); }
        }

        public int Ignored
        {
            get { return ignoredChars; }
        }

        private void Swap(int pos1, int pos2)
        {
            char temp = shuffled[pos1];
            shuffled[pos1] = shuffled[pos2];
            shuffled[pos2] = temp;
        }

        //Determine if a swap between these two would put a letter in a "bad" place
        //If true, a swap is OK. 
        private bool TrySwap(int pos1, int pos2)
        {
            if (original[pos1] == shuffled[pos2] || original[pos2] == shuffled[pos1])
                return false;
            else
                return true;
        }

        //Constructor carries out calls Shuffle function. 
        public ShuffledString(string word)
        {
            original = word;
            shuffled = new StringBuilder(word);
            Shuffle();
            DetectIgnores();
        }

        //Does the hard work of shuffling the string.
        private void Shuffle()
        {
            int length = original.Length;
            int swaps;
            Random rand = new Random();
            List<int> used = new List<int>();

            for (int i = 0; i < length; i++)
            {
                swaps = 0;
                while(used.Count <= length - i)//Until all possibilities have been tried
                {
                    int j = rand.Next(i, length - 1);
                    //If swapping would make a difference, and wouldn't put a letter in a "bad" place,
                    //and hasn't already been tried, then swap
                    if (original[i] != original[j] && TrySwap(i, j) && !used.Contains(j))
                    {
                        Swap(i, j);
                        swaps++;
                        break;
                    }
                    else
                        used.Add(j);//If swapping doesn't work, "blacklist" the index
                }
                if (swaps == 0)
                {
                    //If a letter was ignored (no swap was found), look backward for another change to make
                    for (int k = i; k >= 0; k--)
                    {
                        if (TrySwap(i, k))
                            Swap(i, k);
                    }
                }
                //Clear the used indeces
                used.Clear();
            }
        }

        //Count how many letters are still in their original places.
        private void DetectIgnores()
        {
            int ignores = 0;
            for (int i = 0; i < original.Length; i++)
            {
                if (original[i] == shuffled[i])
                    ignores++;
            }

            ignoredChars = ignores;
        }

        //To allow easy conversion of strings.
        public static implicit operator ShuffledString(string convert)
        {
            return new ShuffledString(convert);
        }
    }

    public class Program
    {
        public static void Main(string[] args)
        {
            ShuffledString[] words = { "abracadabra", "seesaw", "elk", "grrrrrr", "up", "a" };

            foreach(ShuffledString word in words)
                Console.WriteLine("{0}, {1}, ({2})", word.Original, word.Shuffled, word.Ignored);

            Console.ReadKey();
        }
    }
}


using System;
using System.Text;
using System.Collections.Generic;

namespace BestShuffle_RC
{
    public class ShuffledString
    {
        private string original;
        private StringBuilder shuffled;
        private int ignoredChars;

        public string Original
        {
            get { return original; }
        }

        public string Shuffled
        {
            get { return shuffled.ToString(); }
        }

        public int Ignored
        {
            get { return ignoredChars; }
        }

        private void Swap(int pos1, int pos2)
        {
            char temp = shuffled[pos1];
            shuffled[pos1] = shuffled[pos2];
            shuffled[pos2] = temp;
        }

        //Determine if a swap between these two would put a letter in a "bad" place
        //If true, a swap is OK. 
        private bool TrySwap(int pos1, int pos2)
        {
            if (original[pos1] == shuffled[pos2] || original[pos2] == shuffled[pos1])
                return false;
            else
                return true;
        }

        //Constructor carries out calls Shuffle function. 
        public ShuffledString(string word)
        {
            original = word;
            shuffled = new StringBuilder(word);
            Shuffle();
            DetectIgnores();
        }

        //Does the hard work of shuffling the string.
        private void Shuffle()
        {
            int length = original.Length;
            int swaps;
            Random rand = new Random();
            List<int> used = new List<int>();

            for (int i = 0; i < length; i++)
            {
                swaps = 0;
                while(used.Count <= length - i)//Until all possibilities have been tried
                {
                    int j = rand.Next(i, length - 1);
                    //If swapping would make a difference, and wouldn't put a letter in a "bad" place,
                    //and hasn't already been tried, then swap
                    if (original[i] != original[j] && TrySwap(i, j) && !used.Contains(j))
                    {
                        Swap(i, j);
                        swaps++;
                        break;
                    }
                    else
                        used.Add(j);//If swapping doesn't work, "blacklist" the index
                }
                if (swaps == 0)
                {
                    //If a letter was ignored (no swap was found), look backward for another change to make
                    for (int k = i; k >= 0; k--)
                    {
                        if (TrySwap(i, k))
                            Swap(i, k);
                    }
                }
                //Clear the used indeces
                used.Clear();
            }
        }

        //Count how many letters are still in their original places.
        private void DetectIgnores()
        {
            int ignores = 0;
            for (int i = 0; i < original.Length; i++)
            {
                if (original[i] == shuffled[i])
                    ignores++;
            }

            ignoredChars = ignores;
        }

        //To allow easy conversion of strings.
        public static implicit operator ShuffledString(string convert)
        {
            return new ShuffledString(convert);
        }
    }

    public class Program
    {
        public static void Main(string[] args)
        {
            ShuffledString[] words = { "abracadabra", "seesaw", "elk", "grrrrrr", "up", "a" };

            foreach(ShuffledString word in words)
                Console.WriteLine("{0}, {1}, ({2})", word.Original, word.Shuffled, word.Ignored);

            Console.ReadKey();
        }
    }
}

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