readability.c

#include <stdio.h>
#include <cs50.h>
#include <math.h>
#include <string.h>
#include <ctype.h>

// Coleman-Liau index
// L (avg num of letters/100 words)
// S (avg num of sentences/100 words)
// a letter is any uppercase or lowercase alphabetic character
// a word is a character separated by spaces
// period, exclamation point, or question mark indicates the end of a sentence

// isalpha - check whether a character is alphabetical

int main(void)
{
    int sentences = 0, words = 1, letters = 0;
    float L, S, grade;
    string text = get_string("Text:\n");

    for (int i = 0, len = strlen(text); i < len; i++)
    {
        if (isalpha(text[i]))
        {
            letters++;
        }
        else if (text[i] == ' ')
        {
            words++;
        }
        if (text[i] == '.' || text[i] == '!' || text[i] == '?')
        {
            sentences++;
        }
    }
    // printf("Letters: %i\n", letters);
    // printf("Words: %i\n", words);
    // printf("Sentences: %i\n", sentences);

    // round result to the nearest whole number
    L = (float)letters * 100 / (float)words;
    S = (float)sentences * 100 / (float)words;
    grade = round(0.0588 * L - 0.296 * S - 15.8);
    if (grade > 16)
    {
        printf("Grade 16+\n");
    }
    else if (grade < 1)
    {
        printf("Before Grade 1\n");
    }
    else
    {
        printf("Grade %i\n", (int)round(grade));
    }
    return 0;
}