#include <stdio.h>
#include <cs50.h>
#include <ctype.h>
#include <string.h>
#include <stdlib.h>
int main (int argc, string argv[])
{
string plain;
string key;
// Making sure that the command line only accepts two arguments and is a keyword.
if ((argc != 2) && (argc != isalpha(argc)))
// Prints out an error message if the user inputs invalid information.
{
printf("missing command-line argument\n");
return 1;
}
else
{
// Getting the plaintext and the key.
printf("plaintext:");
plain = GetString();
// Key
key = argv[1];
for (int j = 0, len2 = strlen(key); j < len2; j++)
{
for (int i = 0, len = strlen(plain); i < len; i++)
{
if (isalpha (plain[i]))
{
if (isupper (plain[i]))
{
printf("%c", ((plain[i] + key[j]) - 65));
}
if (islower (plain[i]))
{
printf("%c", (((plain[i] + key[j]) - 97) %26) + 97);
}
}
else
{
printf("%c", (plain[i]));
}
}
}
}
printf("\n");
return 0;
}
-
1Please review the following two sites. Pay attention to the section in the second one about naked code drops. Then, please come back and edit your question and add a description of what is happening and perhaps include an example of the bad output. meta.stackexchange.com/questions/22186/… meta.cs50.stackexchange.com/questions/63/…– Cliff BJun 7, 2017 at 2:03
-
Ok thanks very much. I will do that!– Khalil BrackettJun 7, 2017 at 2:54
Add a comment
|
2 Answers
Your for loops are causing you problems. I've commented out the first one and added a j variable which increments every time a isalpha is passed. So now your algorithm is outputting the correct number of characters. But its not ciphering them correctly. You need to use % to wrap around your iteration of the keyword. Watch Zamyla's walkthrough for an explanation.
http://docs.cs50.net/problems/vigenere/vigenere.html
// for (int j = 0, len2 = strlen(key); j < len2; j++)
// {
int j = 0;
for (int i = 0, len = strlen(plain); i < len; i++)
{
if (isalpha (plain[i]))
{
if (isupper (plain[i]))
{
printf("%c", ((plain[i] + key[j]) - 65));
}
if (islower (plain[i]))
{
printf("%c", (((plain[i] + key[j]) - 97) %26) + 97);
}
j++;
}
else
{
printf("%c", (plain[i]));
}
}
There's one more thing to notice in your code which is related to the check for alphabetical arguments :
if ((argc != 2) && (argc != isalpha(argc)))
// Prints out an error message if the user inputs invalid information.
{
printf("missing command-line argument\n");
return 1;
}
Now, the error here is that argc is storing an integer value and isalpha checks that a charachter is alphabetical or not . isalpha function can be used here with argv[1] string to iterate over each charachter to check if it's alphabetical or not. This function returns a boolean value (0/1) depending upon if the condition is false or true and this can be used to execute further statement. Hope that helps! Happy coding!
