caesar.1.c

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

int main(int argc, char* argv[]){
    if (argc != 2){ //check if the user is starting the program properly
        printf("Usage: ./caesar k\n");
        return 1;}
    else{
        printf("plaintext: ");
        string s = get_string();//collect the plaintext from the user
        int n=strlen(s);//stringlenght of the input
        int k = atoi(argv[1]);//convert a the caracter inputed from the user in a int
        for (int i=0; i<n; i++){
            int upper= (isupper(s[i])); //case sensitivity
            int punct=ispunct(s[i]);//check punctuation

            if (upper !=0 ){ //branch for uppercase
                int res_caps = ((int)s[i] - 64 + k);
                int b_caps = (res_caps % 26) + 64; //math to get the alfabetical index
                printf("%c", b_caps);}
            else if (s[i] == ' '){ //branch for spaces
                printf (" ");}
            else if (punct != 0){ //branch for punctuation
                printf("%c", s[i]);}
            else{//branch for lowercase
                int res = ((int)s[i] - 96 + k); //math to get the alfabetical index
                int b = (res % 26) + 96;
                printf("%c", b);}
        }
        printf("\n");

    }



}