How to justify and print a paragraph using a 2d array in C?

Solution 1:

Consider how many spaces you have to distribute. For example, given the input:

18
I am the very model of a modern Major-General.

Computing the number of words that fit on the line goes:

"I" + "am" + "the" + "very"           + (4-1 words) --> 13
"I" + "am" + "the" + "very" + "model" + (5-1 words) --> 19

So only the first 4 words fit on an 18-character line. The number of space characters to distribute are then easily calculated:

N = max_line_width - sum_of_word_lengths

Now for the hard part: how many spaces between each word? Your homework expects you to divvy extra unbalanced spaces left-to-right, meaning that each pair of words may have a different number of space characters.

However, the difference will always be a single space character. Take a moment to convince yourself this is true:

I···am···the··very
-2-4-6-8-0-2-4-6-8

In our little example, we find that there are three space characters in the first two inter-word spacings, and two space characters in the last.

The minimum number of space characters per inter-word spacing is easy enough to caluclate:

nsp = N / (number_of_words_in_line - 1)

^{Beware! What happens if you have only one word on the line? (Do you really need to distribute spaces for such a line?)}

And now, for the cool tricky math part, you can calculate the number of times you need to add a space to the inter-word spacing as:

nplus1 = N - nsp * (number_of_words_in_line - 1)

or just:

nplus1 = N % (number_of_words_in_line - 1)

^{Keep in mind that it is possible that all inter-word spacings are the same number of space characters, and may be exactly one space character even. Notice how our calculations work just as well in those cases.}

Now you can print the words for the line in a loop, adding nsp space characters after every word, plus an extra space after the first nplus1 words.

^{Remember, the last word of the line doesn’t get any spaces. It is followed by a newline!}

Hopefully this should help you work your way through this assignment. (I personally think it is a bit of a careless assignment as your first ever, introduction to C class.)

And now, if I have made errors, it is because I am very, very sleepy. Someone will surely point it out if I have.

Solution 2:

So using Dúthomhas' suggestion I was able to create the function below:

void justifyAndPrintLine(char words[MAX_NUMBER_OF_WORDS][MAX_WORD_LENGTH], int processedWords, int amountOfWordsForNextLine, int lineLength) {
    int total = 0;
    for (int i = processedWords; i < processedWords + amountOfWordsForNextLine; i++) {
        total += (int) strlen(words[i]);
    }
    int spaces = lineLength - total;
    int spacesBetweenWords = spaces / (amountOfWordsForNextLine - 1);
    int spacesRemaining = spaces % (amountOfWordsForNextLine - 1);
    int spaceForThisWord;
    int leftWords = processedWords + amountOfWordsForNextLine;
    while (processedWords != leftWords) {
        spaceForThisWord = spacesBetweenWords;
        if (spacesRemaining > 0) {
            spaceForThisWord++;
            spacesRemaining--;
        }
        printLine(words[processedWords], spaceForThisWord);
        processedWords++;
    }
}

A key part of my understanding of the math was that the difference in spacing was always going to a single space character. Borrowing his math I was able to properly justify the paragraph. Thanks again Dúthomhas!