Question

In C++

Task 2B: User picks an integer in a range and computer guesses using approach similar to binary-search

Enter the left end and right end of a range of integers. User chooses an integer in that range. Computer makes a guess that equals the mid of the range. User gives a feedback for each guess: 1 for too big, 2 for too small and 3 for just right. When the feedback is 1 (too big), the computer throws away any integer that is bigger than guess. When the feedback is 2 (too small), the computer discards the integers any integers that is smaller than the guess. When computer makes a correct guess, the game ends.

Note that your code must ensure a user to entre a feedback in [1, 3].

Sample input/output:

Enter left end in range: 0

Enter right end in range: 10

User has an int in [0, 10]. Computer will guess.

guess #1: 5. How is my guess?

1. too big   2. too small    3. just right

Enter only 1, 2, or 3: 2

guess #2: 8. How is my guess?

1. too big   2. too small    3. just right

Enter only 1, 2, or 3: 1

guess #3: 6. How is my guess?

1. too big   2. too small   3. just right

Enter only 1, 2, or 3: 2

guess #4: The answer must be 7.

Answer 1

#include <iostream>

using namespace std;

int main()

{

    int left, right;

    // read left

    cout << "Enter left end in range: ";

    cin >> left;

    // read right

    cout << "Enter right end in range: ";

    cin >> right;

    // print

    cout << "User has an int in [" << left << ", " << right << "]. Computer will guess.\n";

    int i = 1, guess, feedback;

    // loop till guess is correct

    while (true)

    {

        guess = (left + right) / 2;

        // print guess

        cout << "guess #" << i << ": " << guess << ". How is my guess?\n";

        cout << "1. too big  2. too small  3. just right\n";

        cout << "Enter only 1, 2, or 3: ";

        cin >> feedback;

        // if too big

        if (feedback == 1)

        {

            if (guess == left + 1)

            {

                cout << "guess #" << i + 1 << ": The answer must be " << left << ".\n";

                break;

            }

            right = guess - 1;

        }

        // if too small

        else if (feedback == 2)

        {

            if (guess == right - 1)

            {

                cout << "guess #" << i + 1 << ": The answer must be " << right << ".\n";

                break;

            }

            left = guess + 1;

        }

        // else if guess is correct

        else

        {

            break;

        }

        i++;

    }

    return 0;

}

.

Output:

.