The Errors-
:) substitution.c exists
:) substitution.c compiles
:( encrypts "A" as "Z" using ZYXWVUTSRQPONMLKJIHGFEDCBA as key
output not valid ASCII text
:( encrypts "a" as "z" using ZYXWVUTSRQPONMLKJIHGFEDCBA as key
output not valid ASCII text
:( encrypts "ABC" as "NJQ" using NJQSUYBRXMOPFTHZVAWCGILKED as key
output not valid ASCII text
:( encrypts "XyZ" as "KeD" using NJQSUYBRXMOPFTHZVAWCGILKED as key
output not valid ASCII text
:) encrypts "This is CS50" as "Cbah ah KH50" using YUKFRNLBAVMWZTEOGXHCIPJSQD as key
:) encrypts "This is CS50" as "Cbah ah KH50" using yukfrnlbavmwzteogxhcipjsqd as key
:) encrypts "This is CS50" as "Cbah ah KH50" using YUKFRNLBAVMWZteogxhcipjsqd as key
:) encrypts all alphabetic characters using DWUSXNPQKEGCZFJBTLYROHIAVM as key
:) handles lack of key
:) handles invalid key length
:) handles invalid characters in key
:) handles duplicate characters in key
:) handles multiple duplicate characters in key
The Code-
#include <cs50.h>
#include <stdio.h>
#include <string.h>
#include <ctype.h>
int main(int argc, char* key[])
{
// Vaildate key
int no[26] = {0};
string k = key[1];
if (argc != 2)
{
printf("Enter a key.\n");
return 1;
}
int len = strlen(key[1]);
if (len != 26)
{
printf("Key must contain 26 characters.\n");
return 1;
}
for (int x = 0; x < len; x++)
{
if (islower(k[x]) || isupper(k[x]))
{
no[tolower(k[x])-97] ++;
if (no[tolower(k[x])-97] > 1)
{
printf("Key must have no repeated characters.\n");
return 1;
}
}
else
{
printf("Key needs to contain only letters.");
return 1;
}
}
// Get input
string i = get_string("plaintext: ");
// Encypt input
char output[strlen(i)];
for (int x = 0; x < strlen(i); x++)
if (islower(i[x]))
{
output[x] = tolower(k[i[x] - 97]);
}
else if (isupper(i[x]))
{
output[x] = toupper(k[i[x] - 65]);
}
else
{
output[x] = i[x];
}
// Print output
printf ("ciphertext: %s\n", output);
return 0;
}
