Error implementing Caesar Cipher Using C++ - c++

Question

I am trying to implement Caesar Cipher using C++. The directions are to use this file which is already encrypted:
5
Asi ymj rtrjwfymjx tzylwfgj.
Aqq rnrxd bjwj ymj gtwtlwtajx
Dni ldwj fsi ldrgqj ns ymj bfgj.
Tbfx gwnqqnl fsi ymj xnymjd ytajx
The number 5 represents the shift that is applied to the text. I have to decode the Caesar ciphered text and reverse the lines as in put line 4 in line 1's position and line 3 in line 2's. The first letter of each line does not need to be decoded (the uppercase letters).
The text should look like this after running the program:
Twas brillig and the sithey toves
Did gyre and gymble in the wabe.
All mimsy were the borogroves
And the momerathes outgrabe.
As of right now, I have this code:
#include <iostream>
#include <vector>
#include <string>
#include <fstream>
using namespace std;
char decipher (char c, int shift);
int main(){
//declare variables
char c;
string deciphered = "";
int shift;
vector <string> lines;
//ask for filename and if not found, keep trying
ifstream inFile;
string filename;
cout << "What is the name of the file? ";
cin >> filename;
inFile.open(filename);
while (!inFile){
cout << "File not found. Try again: ";
cin >> filename;
inFile.open(filename);
}
//find shift from file
inFile >> shift;
//get lines from file
inFile >> noskipws;
while (inFile >> c){
char decipheredChar = decipher (c, shift);
deciphered += decipheredChar;
}
cout << deciphered;
}
char decipher (char c, int shift){
string letters = "abcdefghijklmnopqrstuvwxyz";
if (c == 'T'){
return c;
}
else if (c == 'D'){
return c;
}
else if (c == 'A'){
return c;
}
else if (c == ' '){
return c;
}
else {
int currentPosition = letters.find(c);
int shiftedPosition = currentPosition - shift;
if (shiftedPosition < 0){
shiftedPosition = 26 + shiftedPosition;
}
char shifted = letters[shiftedPosition];
return shifted;
}
}
The result I'm getting is this:
uAnd the momerathes outgrabeuuAll mimsy were the borogrovesuDid gyre and gymble in the wabeuuTwas brillig and the sithey tovesu
How do I get rid of the u's and also separate the words by line? I have an idea of reversing the lines using a vector and using a loop counting backwards but I'm not sure how to get to there yet. Please help. Thank you.

Answer 1

To answer your question, the 'u's are the newlines. You read them in and decipher them, so they change and the result is pulled from letters. You should be able to add another case to decipher() to leave newlines alone:
char decipher (char c, int shift){
string letters = "abcdefghijklmnopqrstuvwxyz";
if(c == '\n'){ // do not modify new lines.
return c;
}
else if (c == 'T'){
return c;
}
// ...
}
Probably the cleanest way to reverse the lines is parse them while you read the characters. You can them pop them from the vector in reverse order. A working (but not robust) example would be to add the following to your while loop:
while (inFile >> c){
char decipheredChar = decipher (c, shift);
deciphered += decipheredChar;
if(decipheredChar=='\n'){ //if full line
lines.push_back(deciphered); //push line
deciphered = ""; //start fresh for next line
}
}
lines.push_back(deciphered+'\n'); //push final line (if no newline)
while(!lines.empty()){
cout << lines.back(); //prints last line
lines.pop_back(); //removes last line
}
I say not robust because there are minor things you may still need watch out for. For instance, this reads stores newline from after 5, and if the file ends in a newline I've added an empty one on the end... I'll leave you minor details to clear up.