CS50 Problem Set 2 (Fall 2019) - Substitution

Substitution.c

//CS50 Problem Set 2 (Fall 2019): Substitution
//Author: teeschorle

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

bool validate(string key);

int main(int argc, string argv[])
{
    if (argc == 2)
    {
        string key = argv[1];
        if (validate(key) == true)
        {
            string plaintext = get_string("plaintext: ");
            int charcount = strlen(plaintext);
            char ciphertext[charcount];
            string abc = "abcdefghijklmnopqrstuvwxyz";
            for (int i = 0; i < charcount; i++)
            {
                if (isupper(plaintext[i]) != 0)
                {
                    for (int j = 0; j < 26; j++)
                    {
                        if(abc[j] == tolower(plaintext[i]))
                        {
                            ciphertext[i] = toupper(key[j]);
                            break;
                        }
                    }
                }
                else if (islower(plaintext[i]) != 0)
                {
                    for (int j = 0; j < 26; j++)
                    {
                        if(abc[j] == plaintext[i])
                        {
                            ciphertext[i] = tolower(key[j]);
                            break;
                        }
                    }
                }
                else
                {
                    ciphertext[i] = plaintext[i];
                }
            }
            printf("ciphertext: %s\n", ciphertext);
            return 0;
        }
        else
        {
            printf("Please make sure your key is a permutation of all 26 characters - not more, not less.\n");
            return 1;
        }
    }
    else
    {
        printf("Input error. Please provide a single key.\n");
        return 1;
    }
}

bool validate(string key)
{
    int matches = 0;
    if (strlen(key) == 26)
    {
        for (char c = 'a'; c <= 'z'; c++)
        {
            for (int i = 0; i < 26; i++)
            {
                if(tolower(key[i]) == c)
                {
                    matches++;
                    break;
                }
            }
        }
        if(matches == 26)
        {
            return true;
        }
        else
        {
            return false;
        }
    }
    else
    {
        return false;
    }
}

include <stdio.h>

include <cs50.h>

include <string.h>

include <ctype.h>

bool check(string key);

int main(int argc, string argv[])
{
if (argc == 2)
{

    string key = argv[1];

    if (check(key) == true)
    {

        string text = get_string("Enter plaintext : ");

        int textlenth = strlen(text);

        char cipher[textlenth];

        string alpha = "abcdefghijklmnopqrstuvwxyz";

        for (int j = 0; j < textlenth; j++)
        {
            if (isupper(text[j]) != 0)
            {
                for (int k = 0; k < 26; k++)
                {
                    if (alpha[k] == tolower(text[j]))
                    {
                        cipher[j] = toupper(key[k]);
                        break;
                    }
                }
            }
            else if (islower(text[j]) != 0)
            {
                for (int k = 0; k < 26; k++)
                {
                    if (alpha[k] == text[j])
                    {
                        cipher[j] = tolower(key[k]);
                        break;
                    }
                }
            }
            else
            {
                cipher[j] = text[j];
            }

        }

        cipher[textlenth] = '\0';

        printf("ciphertext: %s\n", cipher);

        return 0;
    }
    else
    {
        printf("Usage: ./substitution key\n");
        return 1;
    }
}
else
{
    printf("Usage: ./substitution key\n");
    return 1;
}

}

bool check(string key)
{
int same = 0;

if (strlen(key) == 26)
{
    for (char c = 'a'; c <= 'z'; c++)
    {
        for (int n = 0 ; n < 26; n++)
        {
            if (tolower(key[n]) == c)
            {
                same++;
                break;
            }
        }
    }

    if (same == 26)
    {
        return true;
    }
    else
    {
        return false;
    }
}
else
{
    return false;
}

}

Thanks! This really help me out this problem

those answers are so long and complicated. Here is my solution:

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

bool check (string s);
bool check (string s)
{
int j, j2;
if (strlen(s) != 26)
{
return false;
}
for (j = 0; j < strlen(s); ++j)
{
for (j2 = j + 1; j2 < strlen(s); ++j2)
{
if (s[j]==s[j2])
{
return false;
}
}
}
for (j = 0; j < strlen(s); ++j)
{
if (isalpha(s[j])==0)
{
return false;
}
}
return true;
}
int main(int c5, string v[])
{
if (c5 != 2)
{
printf ("Wrong Input type. Exp: ./subtitution VcHpRzGjNtLsKfBdQwAxEuYmOi\n");
return 1;
}
int sl = strlen(v[1]);
string cr = v[1];
if (check(v[1])==true)
{
char carr [2][26], c2 [] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
for (int j = 0; j<26;++j)
{
carr[0][j] = cr[j];
carr[1][j] = c2[j];
}
string p2 = get_string("Plain Text: ");
string p3=p2;
int b = 0;
for (;b<strlen(p2); ++b)
{
for (int g = 0; g<26; ++g)
{
if (p2[b] == tolower(carr[1][g]))
{
p3[b] = tolower(carr[0][g]);
break;
}
else if (p2[b] == carr[1][g])
{
p3[b] = toupper((carr[0][g]));
break;
}
else
p3[b] = p2[b];
}
}
printf ("ciphertext: %s\n", p3);
}
else
{
printf ("Key must contain 26 characters.\n");
return 1;
}
}`

Since every one is posting their codes here I thought why not do the same. If some one reads this, please critique on my code so I get better at coding. thankyou :)

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

string ciphertext(string plain, string key);

int main(int argc, string argv[])
{
//To check if arguments are 2 and numeric
if (argc == 2)
{
string key = (argv[1]);
if (strlen(key) == 26) //To check key length
{

        printf("%s\n", key);

        for (int i = 0; (key[i]) != '\0'; i++)
        {
            if (isdigit(key[i])) //To check if key conatains digit
            {
                printf("Key must only cntain alphabetic characters.\n");
                return 1;
            }

            if (isalpha(key[i])) //To check if key is alphabetical //To check if alphabet is double in key
            {
                for (int j = i + 1; key[j] != '\0'; j++)
                {
                    if (key[i] == key[j])
                    {
                        printf("Key must not contain repeated characters.\n");
                        return 1;
                    }
                }
            }
        }
        //main code
        string plain = get_string("plaintext:");
        string cipher = ciphertext(plain, key); //calling function to cipher
        printf("ciphertext: %s\n", cipher);
        return 0;
    }
    else //To check length of key
    {
        printf("Key must contain 26 characters.\n");
        return 1;
    }
}
if (argc != 2) //To check if arguments are 2
{
    printf("Usage: ./substitution key\n");
    return 1;
}

}

string ciphertext(string plain, string key)
{
string c = plain;
string k = key;
string abc = "abcdefghijklmnopqrstuvwxyz";

for (int i = 0; plain[i] != '\0'; i++)
{
    if (islower(plain[i]) != 0)
    {
        for (int j = 0; k[j] != '\0'; j++)
        {
            if (abc[j] == (plain[i]))
            {
                c[i] = tolower(k[j]);
                break;
            }
        }
    }
    else if (isupper(plain[i]) != 0)
    {
        for (int j = 0; k[j] != '\0'; j++)
        {
            if (toupper(abc[j]) == plain[i])
            {
                c[i] = toupper(k[j]);
                break;
            }
        }
    }
    else
    {
        c[i] = plain[i];

    }
}
return c;

}

This function returns a non-zero int if c is an uppercase letter and 0 if c is not an uppercase letter.

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

int main(int argc, string argv[])
{
if (argc != 2 || !isalpha(*argv[1]))
{
printf("Usage: ./sub key\n");
return (1);
}
string key = argv[1];
if (strlen(key) != 26)
{
printf("Usage: ./sub key\n");
return (1);
}
string s = get_string("Plaintext: ");
printf("Ciphertext: ");
for (int i = 0, n = strlen(s); i < n; i++)
{
if (isupper(s[i]))
{
char u = s[i];
char m = 'A';
if (islower(s[i]))
m = 'a';
printf("%c",key[u - m] );
}
else
{
printf("%c",s[i]);
}
}
printf("\n");
return(0);
}

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

bool validate_key(string key);

int main(int argc, string argv[])
{
    //checks if key is the right length
    if (argc != 2 || strlen(argv[1]) != 26 || validate_key((string) argv[1]) != 1)
    {
        printf("Key must exist and contain 26 non identical alphabetical characters.\n");
        return 1;
    }

    //gets input text

    string text = get_string("plaintext: ");

    int len = strlen(text);
    char mychar = toupper(text[0]) - 65;
    for (int i = 0; i < len; i++)
    {
        if (mychar >= 0 && mychar <= 26)
        {
            if (isupper(text[i]))
            {
                text[i] = toupper((char) argv[1][(int) mychar]);
            }
            else
            {
                text[i] = tolower((char) argv[1][(int) mychar]);
            }
        }
        mychar = toupper(text[i + 1]) - 65;
    }

    printf("ciphertext: %s\n", text);
    return 0;
}

bool validate_key (string key)
{
    int len = strlen(key);
    char mychar;
    for(int i = 0; i < len; i++)
    {
        mychar = toupper(key[i]);
        if(mychar >= 65 && mychar <= 90)
        {
            for(int j = i + 1; j < len; j++)
            {
                if(mychar == toupper(key[j]))
                {
                    return 0;
                }
            }
        }
        else
        {
            return 0;
        }
    }
    return 1;
}

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

//get the input from the user in comomand-line
int main (int argc, string argv[])
{
if (argc == 2) // Checks if it is two arugument including file name
{
int len = strlen(argv[1]);

    for (int i = 0; i < len; i++)        //          Checks if it is a digit, if yes, then print the following
    {
        if (isdigit(argv[1][i]))
        {
            printf("Usage: ./substitution key \n");
            exit(0);        //                          To terminate the program immediately
        }
    }
    if (len != 26)       //                          Checks if the length of the given input in command-line is 26 characters, if not, then print
    {
        printf("key must contain 26 characters.");
    }

    string plain = get_string("Plain text: ");      //Get plain text from the user to encode it

    string cipher;
    printf("Cipher text: ");

    for (int i = 0, n = strlen(plain); i < n; i++)
    {
        if (islower(plain[i]))      //              Checks the case sensitive
        {
            printf("%c", tolower(argv[1][plain[i] - 'a'])); // prints lower case cipher calue
        }
        else if (isupper(plain[i]))
        {
            printf("%c", toupper(argv[1][plain[i] - 'A'])); //prints upper case cipher value
        }
        else
        {
            printf("%c", plain[i]);             //          prints apart from alphabetical characters
        }
    }
}

else
{
    printf("Usage: ./substitution key");
}

}