Question

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. In C++

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

C++ code screenshot:

C++ code:

#include <iostream>
#include <limits>
using namespace std;

int main()
{
    int left, right, guessNumber = 1, mid, choice;

    cout << "Enter left end in range: ";
    cin >> left;
    cout << "Enter right end in range: ";
    cin >> right;
    cout << "User has an int in [" << left << ", " << right << "]. Computer will guess.\n";

    while (left < right)
    {
        mid = (left + right) / 2;
        cout << "guess #" << guessNumber << ": " << mid << ". How is my guess?\n";
        cout << "1. too big   2. too small   3. just right \n";
        cout << "Enter only 1, 2, or 3: ";
        cin >> choice;
        while (cin.fail() || choice < 1 || choice > 3)
        {
            //something went wrong, we reset the buffer's state
            cin.clear();
            //and empty it
            cin.ignore(numeric_limits<streamsize>::max(), '\n');

            cout << "\nINVALID INPUT !!! \n";
            cout << "Enter only 1, 2, or 3: ";
            cin >> choice;
        }
        if (choice == 3)
        {
            cout << "\n\nThank You for playing...\n";
            return 0;
        }
        else if (choice == 1)
        {
            right = mid - 1;
        }
        else
        {
            left = mid + 1;
        }
        guessNumber++;
    }
    cout << "guess #" << guessNumber << ": The answer must be " << left << ".\n";
    return 0;
}

Output 1:

Output 2: