Problem with Pset2 submission vigenere

Question

I just wrote the program for cs50 pset2 vigenere problem. It ran perfectly when I tried to run it, with expected output. But on submitting, cs50.me check50 shows that my program does not show the output, when it definitely does.

It runs perfectly. Please help!

#include <stdio.h>
#include <string.h>
#include <ctype.h>
int shift (char c);
int main(int argc, string argv[])
{
 if (argc != 2 || !isalpha(argv[1][0]))
 {
     printf("Usage: ./vignere keyword\n");
     return 1;
 }
 else
 {
     char key[100];
     for(int j=0; key[j] != '\0'; j++)
     {
         key[j] = shift(argv[1][j]);
     }
     string text = get_string("Plaintext: ");
     printf("ciphertext: ");
     int j = 0;
     for (int i = 0; text[i] != '\0'; i++)
     {            
         if (j == strlen(argv[1]))
         {
             j = 0;
         }
         if (islower(text[i]))
         {
             printf("%c",(((text[i] + key[j]) - 97) % 26) + 97);
         }
         else if (isupper(text[i]))
         {
             printf("%c",(((text[i] + key[j]) - 65) % 26) + 65);
         }
         j++;           
     }
     printf("\n");
     return 0;      
 }
}
int shift(char c)
{
 if (islower(c))
 {
     c -= 97;
 }
 else if (isupper(c))
 {
     c -= 65;
 }
 return c;
}

This is the link https://cs50.me/submit50/results/deku82/c9a713dbd8b4c5ed00e196906bbd8f3c23437440

Answer 1

You don't correctly reject keywords which are not completely alphabetic. For that, you'd need a loop over the keyword.

key[j] != '\0' should probably be argv[1][j] != '\0'. That's why input gets printed without any encryption applied.

You don't copy over non-letters. Those should appear unchanged, and not affect the position within the keyword (so in your case not increment j).

An if that returns at the end does not require an else (if you had taken the path, you would never have arrived at the code after the return), could save you some {} and indentation level.