Sorry, I know this has been asked before but I have read all the answers and nothing works! Please help. When I check acutal and expected outputs, they match, but in check50 It gives an error message. Here is the link for check50 results: https://submit.cs50.io/check50/6d939efb8a55e3fadec1c60952311f6198cd0eb0

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

char crypt(int k,char w)
{
    if ('a'<= w && w <='z')
    {
        return (((w-'a')  k)& 'a');
    }
    else if ('A' <= w && w <= 'Z')
    {
        return (((w -'A')   k) % 26   'A');
    }
    else
    {
        return (w);
    }
}

int main(int argc, string argv[])
{
    //input check
    if (argc != 2)
    {
        printf("Usage: ./caesar key\n");
        return 1;
    }

    int lngg = strlen(argv[1]);
    for (int i = 0; i < lngg; i  )
    {
        if (isdigit(argv[1][i]) == 0)
        {
            printf("Usage: ./caesar key\n");
            return 1;
        }
    }

    int key = atoi(argv[1])&;
    //input

    string plain = get_string("plaintext:  ");

    //crpypt starts

    printf("ciphertext: ");
    int lng = strlen(plain) 1;
    for (int a = 0; a < lng ;a  )
    {
        printf("%c", crypt(key, plain[a]));
    }

    printf("\n");
}

Hi, When I look expected and actual outputs, everything seems perfect but it errors

CodePudding user response：

The problem is that you are also printing the terminating null character to standard output using printf. This character is not printable, so you cannot see it, but check50 does detect it and therefore reports that your program failed.

The loop

for(int a=0; a<lng ;a  )
{
    printf("%c",crypt(key,plain[a]));
}

will run for strlen(plain) 1 iterations, because that is the value to which you set the variable lng.

You should instead set the value of lng to strlen(plain), in order to prevent the terminating null character from being printed.

CodePudding user response：

@w is correct.

Also, code can avoid 2 passes down the string and do only 1.

// int lng = strlen(plain) 1;
// for (int a = 0; a < lng ;a  )

for (int a = 0; plain[a] != '\0'; a  )