Algorithm - Numbering for TOC (Table of Contents)

Question

I want to implement a VBA function for Excel row numbers based on the depth of row grouping.

But I think the general TOC generation algorithm is more interesting.

The problem is this:

Given a list of "indentation" such as

One
 Two
  Three
   Four
 Five
Six

(the "indent level" can be considered well-known and part of the input data)

To create the following output:

1.    One
1.1    Two
1.1.1   Three
1.1.1.1  Four
1.2    Five
2.    Six

Of course, my code works and works ... and is also hidden under THWoS (The Heavy Weight of Shame)

Answer 1

Use the stack for numbers. Scroll through each line and check the level of indentation for each line, while not a single indent will be level 1.

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, , JavaScript :

const toc = `
One
 Two
  Three
   Four
 Five
  Six
  Seven
 Eight
Nine
Ten
`;

let stack = [];

toc.trim().split(/\n/g).forEach(line => {
  // Gets the identitation level with 1 being no indentation and so forth
  let level = line.match(/^\s*/)[0].length + 1;

  if (level > stack.length) {
    while (level > stack.length)
      stack.push(1);
  } else {
    while (level < stack.length)
      stack.pop();

    stack[stack.length - 1]++;
  }
  
  let title = stack.join(".") + ". " + line.trim();

  document.body.appendChild(document.createElement("div")).innerText = title;
});

Hide result

Answer 2

, 1 . , "" 1.

#use a vector instead, if your language supports it
numbering = {0, 0, 0, 0, 0, 0, 0}

for line in lines:
    level = indentLevel(line) #starting from 0

    numbering[level] = numbering[level] + 1
    numbering[level + 1] = 0 #create it if it doesn't exist
    for n = 0 to level - 1
        print numbering[n], ".",
    print numbering[level], " ", line