Vigeners cipher -Help needed


I am not sure why the loop iterating over the keyword (j) is not taking the spaces as as when the plain text is taking §Ca someone help me finding out the error.
so if I take an input as ./vigenere bacon
plaintext: Meet me at the park at eleven am
ciphertext: Negh zf gb nal vcld ht mfxcep oz

the expected ouput should be

#include <cs50.h>
#include <stdio.h>
#include <string.h>
#include <ctype.h>
Usage: ./crack hash
single command-line argument: a keyword, k, composed entirely of alphabetical characters.
preserve case
advance to the next leter in the keyword only if it isalpha

int main(int argc, string argv[])
    // ensure proper usage
    if (argc != 2)
        printf("Usage: ./vigenere keyword\n");
        return 1;//error
    //prompt the user to enter the text to be encrypted
    printf("plaintext: ");
    string text = get_string();

    string key = argv[1];
    int len=strlen(key);
    int index_U=0,index_l=0,j=0;
    char c;

    printf("ciphertext: ");
    for(int p=0,n=strlen(text); p<n; p++){
        //printf("key :%c\n",key[j]);

        //ciphertext, c, is computed as:[c = (AI(P) + AI(K)) \bmod 26\] AI-Alphabtical index wherein \(\bmod 26\) here means "remainder when dividing by 26.

        index_U = text[p]-65; // alphabetical index of uppercase letter computed from ascii value of charachters
        index_l=  text[p]-97; // alphabetical index of lowercase letter 
       int key_U = key[j%len]-65; //alpahetical index of key entered
        int key_l =key[j%len]-97;
                //converting alphabetical index to ascii value of charachters to print the ciphered letter 
                    c = (((index_U + key_U )%26)+65); 
                    c = (((index_U + key_l)%26)+65);
            else if (islower(text[p])){
                    c = (((index_l + key_U)%26)+97); 
                    c =(((index_l + key_l)%26)+97); 
        //non-alphabetical characters should be outputted unchanged
            c= text[p];

    return 0;//signifies success



I cleaned up your code.
You need to use triple backticks to post code to the forum.
See this post for details.


I figured it out I was looping through the keyword wrong It should be (isupper(key[j%len]))