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

The provided Java code implements the bestShuffle method, which takes a string as input and returns a shuffled version of that string along with the number of characters that remain in their original positions.

• shuffle(char[] text): This is a helper method that shuffles the characters of a given char array (char[] text) using the Fisher-Yates algorithm. It iterates through each element of the array from the last to the first element, and for each element, it randomly selects another element from the remaining array and swaps their values. This process randomizes the order of the characters in the array.

• bestShuffle(final String s1): This is the main method that performs the "best shuffle" on the given string (s1). It follows a specific logic to find a shuffled version of the string with the least number of characters remaining in their original positions.

  • Converts the input string s1 into a character array s2.

  • Shuffles the character array s2 using the shuffle method.

  • Iterates through the characters of s2 and checks if they are in their original positions compared to s1. If they are, it continues to the next character.

  • If a character in s2 is not in its original position, it searches for another character in s2 that is also not in its original position and is different from the character being examined.

  • If such a character is found, it swaps the positions of the two characters in s2.

  • After the loop, it returns a string representation of s1 followed by the shuffled version in s2 and the count of characters that remained in their original positions (obtained from the count method).

The count method is a helper method that counts the number of characters in a given string (s1) that match the corresponding characters in a given character array (s2).

This code effectively performs a "best shuffle" on the input string by ensuring that the shuffled version has the minimum number of characters in their original positions while still maintaining a randomized order of the characters.

import java.util.Random;

public class BestShuffle {
    private final static Random rand = new Random();

    public static void main(String[] args) {
        String[] words = {"abracadabra", "seesaw", "grrrrrr", "pop", "up", "a"};
        for (String w : words)
            System.out.println(bestShuffle(w));
    }

    public static String bestShuffle(final String s1) {
        char[] s2 = s1.toCharArray();
        shuffle(s2);
        for (int i = 0; i < s2.length; i++) {
            if (s2[i] != s1.charAt(i))
                continue;
            for (int j = 0; j < s2.length; j++) {
                if (s2[i] != s2[j] && s2[i] != s1.charAt(j) && s2[j] != s1.charAt(i)) {
                    char tmp = s2[i];
                    s2[i] = s2[j];
                    s2[j] = tmp;
                    break;
                }
            }
        }
        return s1 + " " + new String(s2) + " (" + count(s1, s2) + ")";
    }

    public static void shuffle(char[] text) {
        for (int i = text.length - 1; i > 0; i--) {
            int r = rand.nextInt(i + 1);
            char tmp = text[i];
            text[i] = text[r];
            text[r] = tmp;
        }
    }

    private static int count(final String s1, final char[] s2) {
        int count = 0;
        for (int i = 0; i < s2.length; i++)
            if (s1.charAt(i) == s2[i])
                count++;
        return count;
    }
}