Chapter 6 // Exercise 8 - Principles & Practice Using C++

In all these exercises I am using Visual Studio Community 2015 and the header file "std_lib_facilities.h" which can be found here:


http://www.stroustrup.com/Programming/PPP2code/std_lib_facilities.h


My version is spelt differently so adjust the code accordingly if copying and pasting.

Chapter 6 // Exercise 8

Redo the "Bulls & Cows" game from exercise 12 in Chapter 5 to use four letters rather than four digits.



#include "stdafx.h"
#include "std_lib_facilities_new_version.h"
using namespace std;

void getSeed();
void printRules();
void startGame();
void getLetters();
void compareLetters();
char assignLoop();
vector<char> fourLetters{ 0,0,0,0 };
vector<char> guess{ 0,0,0,0 };

int main()
try
{
char loop = 'y';

while (loop == 'y')
{
//get number for seed  & assign letters to fourLetters
getSeed();

//print rules of game
printRules();

//begin the game and keep going till user decides to quit
startGame();

//ask if you want to play again
loop = assignLoop();
}

keep_window_open();

return 0;
}


catch (exception& e)
{
cerr << "Error: " << e.what() << '\n';
keep_window_open();
return 1;
}

//produces random number which corralates to ASCII lower case alphabet
char getRandLetter()
{
char randNum = (rand()%(122 - 97 + 1)) + 97; // produces random number between 97 and 122
return randNum;
}

//get seed for rand num and assign letters to comp's four letters
void getSeed()
{
cout << "Please enter a number(any number):\n";
int n;
cin >> n;

srand(n);
for (int i = 0; i < fourLetters.size(); ++i)
{
fourLetters[i] = getRandLetter();
}

sort(fourLetters); //to compare if any are the same

for (int i = 1; i < fourLetters.size(); ++i)
{
while (fourLetters[i] == fourLetters[i - 1])
{
fourLetters[i] = getRandLetter();
}
}

}



void printRules()
{
cout << "//RULES//";
cout << "\nLets Play Bulls & Cows.\n";
cout << "Guess the 4 letters.\n";
cout << "If a letter is right in the right position you will get a bull.\n";
cout << "If the letter is right in the wrong position you will get a cow.\n";
cout << "\nGuess a letter a-z. Each letter must be different and lower case. \n\n";
}

void startGame()
{
while (guess != fourLetters)
{
//get user letters
getLetters();
//compare user and random letters for bulls & cows
compareLetters();
}
}

void getLetters()
{

vector<string>n = { "1st Letter: ", "2nd Letter: ", "3rd Letter: ", "4th Letter: " };

for (int i = 0; i < 4; ++i)
{
cout << n[i];
char letter;
cin >> letter;

if (letter < 'a' || letter > 'z')
error("You can only use lower case.\n");

guess[i] = letter;
}

cout << "Your guess: ";

for (int i = 0; i < 4; ++i)
{
cout << guess[i] << " ";
}

cout << '\n';
}

void compareLetters()
{
for (int i = 0; i < 4; ++i)
{
for (int n = 0; n < 4; ++n)
{
if (guess[i] == fourLetters[n])
{
if (i == n)
cout << "1 Bull(" << guess[i] << ")";
else
cout << "1 Cow(" << guess[i] << ")";
}
}
}
}

char assignLoop()
{
cout << "\n\nCongratz! You did it!\n";
cout << "Would you like to play again? y / n:\n";
char l;
cin >> l;
while (l != 'y' && l != 'n')
{
cout << "Invalid answer, try again. y / n:\n";
cin >> l;
}

return l;
}

This one took a while as I figured out how to perfect a few things. The original exercise had you guess a number 1 - 9, this one a letter a -z. Since int and char are interchangeable I simply changed most of the code to char however when it came to randomizing what letters you would get I had to find a new function.

The one I've got accepts a max and a min value, for us we want between 97 and 122 as these are the numbers for the characters a - z. I then just assigned one of the generated numbers to the guess vector. When looking to see if any of them were the same I realised my prior function wasn't exactly perfect and would sometimes allow the same numbers. I've corrected it on this one by sorting them first. This does give the letters some predictability by putting them in order however not all the time as if some are the same they will be changed to another generated number.