encrypt

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

int         is_lower(char c) {
    return (c >= 'a' && c <= 'z');
}

int         is_upper(char c) {
    return (c >= 'A' && c <= 'Z');
}

char        *encrypt_with_number_key(char *str, int key) {
    int     i = 0;

    while(str[i])
    {
        if(is_lower(str[i])){
            str[i] = (str[i] - 'a'  + key)%26 + str[i];
        }
        else if(is_upper(str[i])){
            str[i] = (str[i] - 'A'  + key)%26 + str[i];
        }
        i++;
    }
    return str;
}

char        *encrypt_with_string_key(char *str, char key[]){
    int     i = 0;

    while(str[i])
    {
        if(is_lower(str[i])){
            str[i] = str[i] + ((str[i] - 'a') +
            is_lower(key[i%strlen(key)]) ? key[i%strlen(key)] - 'a' :  is_upper(key[i%strlen(key)]) ? key[i%strlen(key)] - 'A': 0)%26 ;
        }
        else if(is_upper(str[i])){
            str[i] = str[i] + ((str[i] - 'A') +
            is_lower(key[i%strlen(key)]) ? key[i%strlen(key)] - 'a' :  is_upper(key[i%strlen(key)]) ? key[i%strlen(key)] - 'A': 0)%26 ;

        }
        i++;
    }
    return str;
}


int             main(int argc, char **argv)
{
    if(argc == 4)
    {
        if(atoi(argv[3]) == 0)
        {

            char *s = encrypt_with_number_key(&argv[1][0], atoi(argv[2]));
            printf("String:%s\nCipher:%s\n",argv[1], s);
        }

        if(atoi(argv[3]) == 1)
        {

            char *s = encrypt_with_string_key(&argv[1][0], argv[2]);
            printf("String:%s\nCipher:%s\n",argv[1],s);
        }

    }
    return (0);
}