我通过将num初始化为1来解决这个问题，因为这是我所知道的获得实际单词计数的唯一方法。但我不明白这背后的逻辑，在不了解发生了什么的情况下修复它不是一个好的做法。还有，我怎么发代码，它一直告诉我“看起来你的帖子大部分都是代码;请多加一些细节。”但是我没有别的要写了…

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

int count_letters(string text);
int count_words(string text);
int count_sentences(string text);

int main(void)
{
    string input; // get input, making sure it does not start with space
    do
    {
        input = get_string("Text: ");
    }
    while (input[0] == ' ');

    // CALCULATION
    int letters = count_letters(input);
    int words = count_words(input);
    int sentences = count_sentences(input);

    float L =
        ((float) letters / words) * 100; // need float or it will truncate removing the remainder as it is two int getting divided
    float S = ((float) sentences / words) * 100;

    int index = round(0.0588 * L - 0.296 * S - 15.8);

    if (index > 16)
    {
        printf("Grade 16+\n");
    }

    else if (index < 1)
    {
        printf("Before Grade 1\n");
    }

    else
    {
        printf("Grade %i\n", index);
    }
}

int count_letters(string text)
{
    int num = 0;

    for (int i = 0, l = strlen(text); i < l; i++)
    {
        if (isalpha(text[i]))
        {
            num++;
        }
    }
    return num;
}

int count_words(string text)
{
    int num = 1; // number should start from 1 for our purpose????? maybe the

    for (int i = 0, l = strlen(text); i < l; i++)
    {
        if (isspace(text[i]))
        {
            num++;
            if (isspace(text[i + 1])) // eliminating double spaces in between sentences
            {
                num--;
            }
        }
    }
    return num;
}

int count_sentences(string text)
{
    int num = 0;

    for (int i = 0, l = strlen(text); i < l; i++)
    {

        if (text[i] == '?')
        {
            num++;
        }
        if (text[i] == '!')
        {
            num++;
        }
        if (text[i] == '.')
        {
            num++;
        }
    }
    return num;
}