i trying implement caesar cipher using c++. directions use file 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 shift applied text. have decode caesar ciphered text , reverse lines in put line 4 in line 1's position , line 3 in line 2's. first letter of each line not need decoded (the uppercase letters).
the text should after running program:
twas brillig , sithey toves did gyre , gymble in wabe. mimsy borogroves , momerathes outgrabe. as of right now, have 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 filename , if not found, keep trying ifstream infile; string filename; cout << "what name of file? "; cin >> filename; infile.open(filename); while (!infile){ cout << "file not found. try again: "; cin >> filename; infile.open(filename); } //find shift file infile >> shift; //get lines 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 this:
uand momerathes outgrabeuuall mimsy borogrovesudid gyre , gymble in wabeuutwas brillig , sithey tovesu how rid of u's , separate words line? have idea of reversing lines using vector , using loop counting backwards i'm not sure how there yet. please help. thank you.
to answer question, 'u's newlines. read them in , decipher them, change , result pulled letters. should able add case decipher() leave newlines alone:
char decipher (char c, int shift){ string letters = "abcdefghijklmnopqrstuvwxyz"; if(c == '\n'){ // not modify new lines. return c; } else if (c == 't'){ return c; } // ... } probably cleanest way reverse lines parse them while read characters. can them pop them vector in reverse order. working (but not robust) example add following 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 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 not robust because there minor things may still need watch out for. instance, reads stores newline after 5, , if file ends in newline i've added empty 1 on end... i'll leave minor details clear up.
Comments
Post a Comment