CS50's Problem Set 2 - Readablity

readability.c

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


int main(void)
{
    string text = get_string("Text:");

    int letterCount = 0;
    int wordCount = 1;
    int sentenceCount = 0;

    for(int i = 0, len = strlen(text); i < len; i++) 
    {
        if(isalpha(text[i])) 
        {
           letterCount++;
        }
        else if (isspace(text[i])) 
        {
            wordCount++;
        }
        else if(text[i] == '.' || text[i] == '!' || text[i] == '?')
        {
            sentenceCount++;
        }

    }

    float L = (float)letterCount / (float) wordCount * 100;
    float S = (float) sentenceCount / (float) wordCount * 100;

    float index = 0.0588 * L - 0.296 * S - 15.8;

    if (index < 1) 
    {
        printf("Before Grade 1\n");
    }
    else if (index > 16) 
    {
        printf("Grade 16+\n");
    }
    else 
    {
        printf("Grade %i\n", (int) round(index));
    }
}