# PE2 (AY24/25)

## Problems

### 2. Thesis

> A classic string manipulation problem.

My solution is to insert the `\n` at the proper white space to make sure we've excluded the leading and trailing spaces.

{% code lineNumbers="true" %}

```c
void wrap(char *line, long limit)
{
  size_t len = strlen(line);
  long one_ahead_len = 0;
  long next_length = 0;
  for (long i = 0; i < (long)len;)
  {
    next_length = next_word_length(line, i);
    one_ahead_len += next_length;
    if (one_ahead_len > limit)
    {
      if (line[i] != ' ')
      {
        line[i-1] = '\n';
      }
      else
      {
        line[i] = '\n';
        i += 1;
      }
      one_ahead_len = 0;
      continue;
    }
    i += next_length;
  }
  print_line(line);
}
```

{% endcode %}

The idea is that, `i` represents **the starting character of a word of a white space**, `one_ahead_len` stores **the length of the current line plus one word or white space** [**ahead**](#user-content-fn-1)[^1]. And every time, we first get the next word length, which will return 1) 1 if `line[i]` is a space 2) the length of the word if it is the start of a word. It is implemented as follows:

{% code lineNumbers="true" %}

```c
long next_word_length (char *line, long i)
{
  long len = 0;
  if (line[i] == ' ')
  {
    return 1;
  }
  while (line[i] != ' ' && line[i] != 0)
  {
    len += 1;
    i += 1;
  }
  return len;
}
```

{% endcode %}

Let's continue, if the `curr_len` is bigger than `limit`, then we need to wrap by replacing the white space character with `\n` character. Now, let's see Line 12 to Line 19, this indicates that there are two cases when we wrap the line, it is 1) either you are **at the start of a word** 2) or you are **at the start of a white space**. In the first case, we should replace the white space which is exactly one position before `i` (`line[i-1]`) with `\n` while in the second case, we should replace the `line[i]` with `\n` and increment `i` by 1 to let it point to the next starting position of a word.

After we have done setting our `\n`, we set `one_ahead_len = 0` and skip the increment of `i += next_length` because we haven't started dealing with the word starting at `i`.

In the normal case where `one_ahead_line <= limit`, we don't need to do anything and just need to set `i += next_length`

## Tips

1. When doing string traversal using **while** loop, always add **current character is not equal to `\0` as one of its terminating condition**!

[^1]: Here "ahead" means the word


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