caesar.cpp

/*************************
 * Name: Brian Stamm
 * Date: 2.1.15
 * Description: This is caesar.cpp. 1 of 1. This is a simple encoding program
 * that takes an entered cstring from the user and then spits out
 * an encoded one.
 *************************/

#include <iostream>
#include<cstring>
#include <string>

using namespace std;

char alpha[27] ="abcdefghijklmnopqrstuvwxyz"; //Key for the encoding

string encipher(int, char *a); //Proto function, more below

int main(){

 int offset;
 char words[100];
 string newPhrase;
//Basic instructions
 cout <<"This is a simple encoding program called a Caesar cipher." <<endl;
 cout <<"It will ask you for a phrase, and then translate that into" <<endl;
 cout <<"a code NO ONE can crack! Then it will ask for how big of" <<endl;
 cout <<"an offset from a you want. If you pick 1, a will be replace" <<endl;
 cout <<"b. If you pick two, a would be replaced by c, and so forth." <<endl;
 cout <<"Enjoy!" <<endl;
 cout <<endl;

 //Getting the phrase user wants to translate
 cout << "What would you like to use as a string: ";
 cin.getline(words, 100);
 
 //Getting the offset
 cout <<endl;
 cout <<"What would you like the offset to be: ";
 cin >> offset;

//Function that returns the new phrase
 newPhrase = encipher(offset, words);
 
 //Returning the new phrase
 cout <<endl;
 cout << "New phrase: " <<endl;
 cout << newPhrase << endl;
 
 return 0;
}
/*****
 * This function will cycle through each character of the cstring the user
 * inputted, and depending on the value of it, it will either replace it
 * or just reinsert the character.
 * parameters: int and array, int is the offset user wants for the coding
 * and the array is the cstring.
 * ********/


string encipher(int change, char *phrase){
 int i, j, k, diff; //each are counters or holders
 string newPhrase = ""; //the string to hold the new phrase the is enciphered
 for (i = 0; i<= strlen(phrase); i++){ //loop to go through cstring w/i
 char temp;
 temp = phrase[i]; //takes character out of string at i into holder
 if (isalpha(temp)){ //If string that tests what the temp is, first if an alphabet
	 if(islower(temp)){ //then if it's lower case 
	 for (j=0; j<= strlen(alpha); j++){ //Loop to go through key w / j
		 if (alpha[j] == temp){ //Determines place of letter in key
		 k = j; 
		 k += change; //sets new int as new position for new phrase
		 if (k > 25){ //if statement in case if offset larger than z
			diff = k - 25;
			temp = alpha[diff - 1]; //Replaces temp with new letter
			newPhrase += temp; //Adds new letter to holder string
			break;// break to do it again.
		 }
		 else{ // Else statment if offset not more than z
			temp = alpha[k];
			newPhrase +=temp;
			break;
		 }}}}
	 else if(isupper(temp)){ //Same type of loop as above, but for upper case
	 temp = tolower(temp); // makes it lower case for the key and to replace 
	 for (j=0; j<= strlen(alpha); j++){ //with upper before put in string
		 if (alpha[j] == temp){
		 k = j;
		 k+= change;
		 if (k > 25){
			diff = k - 25;
			temp = alpha[diff - 1];
			newPhrase += temp;
			break;
		 }
		 else{
			temp = alpha[k];
			newPhrase += toupper(temp);
			break;
		 }}} 
		 }}
 else if (isdigit(temp)){ //If a digit, replaces with same digit
	 newPhrase += temp;
	 }
 else if (ispunct (temp)){//Same as above, puncutation
 newPhrase += temp;
 }
 else if (isspace(temp)){//Same, whitespace
 newPhrase += temp;
 }
 }
 return newPhrase; //returns the phrase when done
}