Step by Step solution about How to resolve the algorithm Move-to-front algorithm step by step in the Julia programming language

The provided Julia code implements the Move-to-Front (MTF) encoding and decoding algorithms. MTF is a simple and efficient compression algorithm based on the idea of moving the most recently seen character to the front of a symbol table.

Encoding Function (encodeMTF) The encodeMTF function takes two arguments:

• str: The input string to be encoded.
• symtable: An optional vector of characters representing the symbol table. By default, it contains the lowercase letters 'a' to 'z'.

The encoding process involves the following steps for each character in the input string:

1. Find the index of the character in the symbol table (r).
2. Delete the character from its current position in the symbol table.
3. Prepend the character to the front of the symbol table.
4. Return the index r as the encoded value.

Decoding Function (decodeMTF) The decodeMTF function takes two arguments:

• arr: A vector of integers representing the encoded string.
• symtable: An optional symbol table. By default, it is the same as in the encoding process.

The decoding process involves the following steps for each index in the encoded vector:

1. Look up the character in the symbol table at the given index.
2. Delete the character from its current position in the symbol table.
3. Prepend the character to the front of the symbol table.
4. Return the character as the decoded value.

To demonstrate the encoding and decoding, the code initializes a testset with three strings. Then, it encodes each string using encodeMTF, stores the encoded results in encoded, and decodes the encoded results using decodeMTF, storing the decoded results in decoded.

Finally, the code prints the original string, the encoded string, and the decoded string for each test case. It also includes a test script to verify that the decoded strings are equal to the original strings.

In summary, this code provides a straightforward implementation of the MTF encoding and decoding algorithms for data compression.

function encodeMTF(str::AbstractString, symtable::Vector{Char}=collect('a':'z'))
    function encode(ch::Char)
        r = findfirst(symtable, ch)
        deleteat!(symtable, r)
        prepend!(symtable, ch)
        return r
    end
    collect(encode(ch) for ch in str)
end

function decodeMTF(arr::Vector{Int}, symtable::Vector{Char}=collect('a':'z'))
    function decode(i::Int)
        r = symtable[i]
        deleteat!(symtable, i)
        prepend!(symtable, r)
        return r
    end
    join(decode(i) for i in arr)
end

testset = ["broood", "bananaaa", "hiphophiphop"]
encoded = encodeMTF.(testset)
decoded = decodeMTF.(encoded)
for (str, enc, dec) in zip(testset, encoded, decoded)
    println("Test string: $str\n -> Encoded: $enc\n -> Decoded: $dec")
end

using Base.Test
@testset "Decoded string equal to original" begin
    for (str, dec) in zip(testset, decoded)
        @test str == dec
    end
end