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Developing Guess game in C++ step by step

Objectives: learn loops, input/output, if statement, random numbers

In this article we will develop Guess game step by step. The rules of the game is quite simple:

  • Computer proposes number in range 1..1000 and a player should guess it.
  • At every step of the game, player tells to the computer his assumption about a number and computer tells, if player guessed it right. Otherwise, computer tells the player if his number is less or more, than the proposed number and player tries again.

Main function

First of all we should write a correct main function:

int main() {

      return 0;

}

Propose a number

Then the computer should propose a number. We will do it, using rand() function. It returns a number in range from 0 to RAND_MAX (which is quite big). In order to put the number in 1..1000 range, we can use remainder operator:

#include <cstdlib>

 

int main() {

      int number;

      number = rand() % 1000 + 1;

      return 0;

}

cstdlib library is required in order to use rand() function.

Ask player for his guess

Next, we should ask player for his guess.

#include <cstdlib>

#include <iostream>

 

using namespace std;

 

int main() {

      int number;

      number = rand() % 1000 + 1;

      int guess;

      cout << "Enter your estimate: ";

      cin >> guess;

      return 0;

}

iostream library allows us to use input/output functions.

Compare player's estimate with the proposed number

Compare player's estimate with the secret number and tell him the result.

#include <cstdlib>

#include <iostream>

 

using namespace std;

 

int main() {

      int number;

      number = rand() % 1000 + 1;

      int guess;

      cout << "Enter your estimate: ";

      cin >> guess;

      if (guess < number)

            cout << "Your estimate is less, than the secret number" << endl;

      else if (guess > number)

            cout << "Your estimate is more, than the secret number" << endl;

      else

            cout << "Your guess is right!" << endl;

      system("PAUSE");

      return 0;

}

 

The line: system("PAUSE"); prevents console window from closing.

Keep asking

If player didn't guess the secret number right, the program should keep asking him:

#include <cstdlib>

#include <iostream>

 

using namespace std;

 

int main() {

      int number;

      number = rand() % 1000 + 1;

      int guess;

      do {

            cout << "Enter your estimate: ";

            cin >> guess;

            if (guess < number)

                  cout << "Your estimate is less, than the secret number" << endl;

            else if (guess > number)

                  cout << "Your estimate is more, than the secret number" << endl;

            else

                  cout << "Your guess is right!" << endl;

      } while (guess != number);

      system("PAUSE");

      return 0;

}

 

Now the game is complete. Last step to make it shine, is to change random seed. Actually, rand() function always returns the same number and it makes the game boring. To change the seed, we should call srand function.

 

#include <cstdlib>

#include <time.h>

#include <iostream>

 

using namespace std;

 

int main() {

      srand(time(0));

      int number;

      number = rand() % 1000 + 1;

      int guess;

      do {

            cout << "Enter your estimate: ";

            cin >> guess;

            if (guess < number)

                  cout << "Your estimate is less, than the secret number" << endl;

            else if (guess > number)

                  cout << "Your estimate is more, than the secret number" << endl;

            else

                  cout << "Your guess is right!" << endl;

      } while (guess != number);

      system("PAUSE");

      return 0;

}

Final source code

#include <cstdlib>

#include <time.h>

#include <iostream>

 

using namespace std;

 

int main() {

      srand(time(0));

      int number;

      number = rand() % 1000 + 1;

      int guess;

      do {

            cout << "Enter your estimate: ";

            cin >> guess;

            if (guess < number)

                  cout << "Your estimate is less, than the secret number" << endl;

            else if (guess > number)

                  cout << "Your estimate is more, than the secret number" << endl;

            else

                  cout << "Your guess is right!" << endl;

      } while (guess != number);

      system("PAUSE");

      return 0;

}


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