Building a nested array

Question

I have an outline format text document that can have up to 6 levels.

.step1 -- step 1. text
..step2 -- step 1. A. text
..step2 -- step 1. B. text
..step2 -- step 1. C. text
..step2 -- step 1. D. text
..step2 -- step 1. E. text
.step1 -- step 2. text
..step2 -- step 2. A. text
...step3 -- step 2. A. (1) text
...step3 -- step 2. A. (2) text
.step1 -- step 3. text

I'm parsing the text document with regex and building an array that is structured like this

$contentsArray structure
    'level' INT - the step level
    'type'  STRING - the type of tag, note, warning, step1, step2
    'line'  INT - the line number in the file
    'text'  STRING - the text

 ------ SAMPLE ARRAY -------

   [0] => Array
    (
        [level] => 1
        [type] => step1
        [line] => 8
        [text] => Step 1. text
    )

[1] => Array
    (
        [level] => 2
        [type] => step2
        [line] => 10
        [text] => Step 1. A. text
    )

[2] => Array
    (
        [level] => 2
        [type] => step2
        [line] => 12
        [text] => Step 1.B. text
    )

[3] => Array
    (
        [level] => 2
        [type] => step2
        [line] => 14
        [text] => Step 1. C. text.
    )

[4] => Array
    (
        [level] => 2
        [type] => step2
        [line] => 16
        [text] => Step 1. D. text.
    )

[5] => Array
    (
        [level] => 2
        [type] => step2
        [line] => 18
        [text] => Step 1. E. text.
    )

[6] => Array
    (
        [level] => 1
        [type] => step1
        [line] => 20
        [text] => Step 2. text
    )

[7] => Array
    (
        [level] => 2
        [type] => step2
        [line] => 22
        [text] => Step 2. A. Text.
    )

[8] => Array
    (
        [level] => 3
        [type] => step3
        [line] => 26
        [text] => Step 2. A. (1) Text.
    )

[9] => Array
    (
        [level] => 3
        [type] => step3
        [line] => 28
        [text] => Step 3. A. (2) Text.
    )

[10] => Array
    (
        [level] => 1
        [type] => step1
        [line] => 30
        [text] => Step 3. Text
    )

The end goal is to turn this into a nested XML document.

<step1>Step 1. text
   <step2>Step 1. A. text</step2>
   <step2>Step 1. B. text</step2>
   <step2>Step 1. C. text</step2>
   <step2>Step 1. D. text</step2>
   <step2>Step 1. E. text</step2>
</step1>
<step1>Step 2. text
   <step2>Step 2. A. text
     <step3>Step 2. A. (1) text</step3>
     <step3>Step 2. A. (2) text</step3>
   </step2>
</step1>
<step1>Step 3. text
</step1>

I think that what I need is to build a nested array that I can then convert into the XML. I think the structure for this array would be something like

   [0] => Array
        (
            [level] => 1
            [type] => step1
            [line] => 8
            [text] => Step 1. text
        ), Array
            (
                [level] => 2
                [type] => step2
                [line] => 10
                [text] => Step 1. A. text
            ), Array
            (
                [level] => 2
                [type] => step2
                [line] => 12
                [text] => Step 1.B. text
            ), Array
            (
                [level] => 2
                [type] => step2
                [line] => 14
                [text] => Step 1. C. text.
            ), Array
            (
                [level] => 2
                [type] => step2
                [line] => 16
                [text] => Step 1. D. text.
            ), Array
            (
                [level] => 2
                [type] => step2
                [line] => 18
                [text] => Step 1. E. text.
            )
        )
    [1] => Array
        (
            [level] => 1
            [type] => step1
            [line] => 20
            [text] => Step 2. text
        , Array
            (
                [level] => 2
                [type] => step2
                [line] => 22
                [text] => Step 2. A. Text.
                , Array
                (
                    [level] => 3
                    [type] => step3
                    [line] => 26
                    [text] => Step 2. A. (1) Text.
                ), Array
                (
                    [level] => 3
                    [type] => step3
                    [line] => 28
                    [text] => Step 3. A. (2) Text.
                )
            )
        )

    [2] => Array
        (
            [level] => 1
            [type] => step1
            [line] => 30
            [text] => Step 3. Text
        )

What I need is some help on a method to loop through the array that I have built and use the level value to figure out the nesting in the final array. My attempts have been pretty fruitless to this point. I feel like there is a recursive or iterator way to do this but these aren't my strong suit.

Thanks for the help and I hope this question is clear enough.

UPDATE THE QUESTION I see I did a pretty poor job of asking the question so I have made some edits.

If you're using PHP you should tag the question with 'php' tag — Nir Alfasi
– Nir Alfasi, Commented May 19, 2017 at 19:26
I am doing this in PHP but to me this is more of a technique question. — Sports Racer
– Sports Racer, Commented May 19, 2017 at 19:39
You describe an associative array with 4 properties, but where is the "text" part in your input, and how come your array just has a "text" property and not the other 3? — trincot
– trincot, Commented May 19, 2017 at 20:26

Gene · Accepted Answer · 2017-05-19 20:19:03Z

1

Your example isn't consistent. Assuming the last ...step3 is a mistake, this will do what you want. It's in perl, but should easily translate.

sub main {
  my @labels;
  while (<>) {
    if (/^(\.+)(.*)$/) {
      my $level = length($1);
      print "</" . pop(@labels) . ">\n" while $level <= scalar(@labels);
      die "Bad input" unless $level == 1 + scalar(@labels);
      print "<" . $2 . ">\n";
      push @labels, $2
    }
  }
  print "</" . pop(@labels) . ">\n" while (@labels);
}

main;

It's using a simple stack and processing level changes with respect to current stack size.

I'll let you work out the indentation. You can do this based on stack size, too.

Addition

Well, you've changed the question quite a bit. But the basic approach of using a stack and processing level changes with respect to stack length will still work fine.

edited May 19, 2017 at 20:19

answered May 19, 2017 at 19:52

Gene

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trincot · Accepted Answer · 2017-05-19 21:24:50Z

1

Here is PHP implementation for when you have the input text in a variable $input:

$stack = [];
foreach(explode("\n", $input . "\n.") as $line) {
    $line = trim($line);
    $type = ltrim($line, ".");
    $dots = strlen($line) - strlen($type);
    if (!$dots || $dots > count($stack) + 1) throw new Exception("Bad input format");
    while($dots <= count($stack)) 
        $xml[] = str_repeat("    ", count($stack)-1) . array_pop($stack);
    $xml[] = str_repeat("    ", count($stack)) . "<$type>";
    $stack[] = "</$type>";
}
$xml = implode("\n", array_slice($xml, 0, -1));
echo $xml;

See it run on eval.in.

answered May 19, 2017 at 21:24

trincot

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