CS50 Pset2 Substitution

substitution.c

/*
CS50 Substitution
araidz
*/

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

int main(int argc, string argv[])
{
    // Declare the variables
    int key_len, text_len, i, j;
    string plain_text, key;

    if (argc != 2)
    {
        printf("Usage: ./substitution key\n");
        return 1;
    }

    // Assign the key to variable key
    key = argv[1];
    // Get the length of the key
    key_len = strlen(argv[1]);

    if (key_len != 26)
    {
        // Check if key is 26 letters
        printf("Key must contain 26 characters.\n");
        return 1;
    }
    else
    {
        for (i = 0; i < key_len; i++)
        {
            // Check if char is not a letter
            if (!isalpha(key[i]))
            {
                printf("Key must contain 26 characters.\n");
                return 1;
            }

            for (j = i + 1; j < key_len; j++)
            {
                // Check if char is not a duplicate
                if (key[i] == key[j])
                {
                    printf("Key must contain 26 characters.\n");
                    return 1;
                }
            }
        }

        // Get user input for plaintext
        plain_text = get_string("plaintext: ");

        // Get the length of the plaintext
        text_len = strlen(plain_text);

        printf("ciphertext: ");

        // Store ciphertext in a variable
        char cipher_text[text_len];

        // Iterate through each char in the plaintext
        for (i = 0; i < text_len; i++)
        {
            // Check if char is a letter
            if (isalpha(plain_text[i]))
            {
                // Check if letter is upeer
                if (isupper(plain_text[i]))
                {
                    cipher_text[i] = toupper(key[plain_text[i] - 65]);
                }
                // Check if letter is lower
                else if (islower(plain_text[i]))
                {
                    cipher_text[i] = tolower(key[plain_text[i] - 97]);
                }
            }
            // Check if char is not a letter
            else
            {
                cipher_text[i] = plain_text[i];
            }
        }
        // Print a new line after ciphertext
        printf("%s\n", cipher_text);
    }
}