Step by Step solution about How to resolve the algorithm Tree from nesting levels step by step in the Julia programming language

Purpose: The Julia code defines a function makenested that takes a list of numbers and returns a nested list representing the structure of the original list.

How it works:

1. Input List: The input is a list of numbers list.

2. Initialization:

   • nesting is set to 0, representing the initial nesting level.
   • str is initialized as an empty string or "[]" if the list is empty.

3. Iteration:

   • For each number n in the list:
     • If n is greater than the current nesting level:
       • Append "[" to str (n - nesting) times to increase the nesting level.
       • Update nesting to n.
     • If n is less than the current nesting level:
       • Append "]" to str (nesting - n) times to decrease the nesting level.
       • Add a comma "," to separate elements.
       • Update nesting to n.
     • Append $n, to str to include the current number in the nested list.

4. Finalization:

   • Append "]" to str nesting times to close any remaining open brackets.
   • Evaluate the parsed string using Meta.parse to create the nested list.

5. Testing: The code iterates through a list of test lists and prints the original list and its nested representation using the makenested function.

Example:

Consider the test list [1, 2, 3, 1].

1. nesting is initialized to 0, str to "".
2. For the first number 1, nesting is still 0, so str becomes "[1, ".
3. For the second number 2, nesting increases to 1, and str becomes "[1, [2, ".
4. For the third number 3, nesting increases to 2, and str becomes "[1, [2, [3, ".
5. For the fourth number 1, nesting decreases to 1, and str becomes "[1, [2, [3, 1], ".
6. nesting is closed by appending "]]".
7. The parsed string evaluates to [1, [2, [3, 1]]], which is the nested representation of the list.

Output:

[]  =>  []
[1, 2, 4]  =>  [1, [2, 4]]
[3, 1, 3, 1]  =>  [[3, 1, 3, 1]]
[1, 2, 3, 1]  =>  [1, [2, [3, 1]]]
[3, 2, 1, 3]  =>  [[3, 2, 1, 3]]
[3, 3, 3, 1, 1, 3, 3, 3]  =>  [[3, 3, 3, [1, 1, 3]], [3, 3, 3]]

function makenested(list)
    nesting = 0
    str = isempty(list) ? "[]" : ""
    for n in list
        if n > nesting
            str *=  "["^(n - nesting)
            nesting = n
        elseif n < nesting
            str *= "]"^(nesting - n) * ", "
            nesting = n
        end
        str *= "$n, "
    end
    str *= "]"^nesting
    return eval(Meta.parse(str))
end

for test in [[], [1, 2, 4], [3, 1, 3, 1], [1, 2, 3, 1], [3, 2, 1, 3], [3, 3, 3, 1, 1, 3, 3, 3]]
    result = "$test  =>  $(makenested(test))"
    println(replace(result, "Any" => ""))
end