Exercise 2-9

Write a program that asks the user to enter two numbers and tells the user which number is larger than the other.

Solution

Here is my solution strategy:

• Obtain the two numbers from user. i.e. a and b.
• Perform a condition check. There are 3 possible cases.
• Case 1: a == b
• Case 2: a > b
• Case 3: a < b
• Prepare the outcome of each case. e.g. each case can have its own output message.

Putting this together, we have our full program.

#include <iostream>
using std::cout;
using std::cin;
using std::endl;

int main()
{
    cout << "***********************************************************************\n"
         << "*** This program compare 2 numbers and tell you which one is larger ***\n"
         << "***********************************************************************\n";
    cout << endl;
    cout << "Enter the first number (a): ";
    int a;
    cin >> a;
    cout << "Enter the second number (b): ";
    int b;
    cin >> b;
    cout << "a = " << a << ", b = " << b << endl;
    if (a == b)
        {cout << "a == b";}
    else if (a > b)
        {cout << "a > b";}
    else
        {cout << "a < b";}
    return 0;
}

Result

Let’s supply 3 sets of input (representing the 3 cases) and confirm the condition check works.

Case 1: a == b

***********************************************************************
*** This program compare 2 numbers and tell you which one is larger ***
***********************************************************************

Enter the first number (a): 5
Enter the second number (b): 5
a = 5, b = 5
a == b

Case 2: a > b

***********************************************************************
*** This program compare 2 numbers and tell you which one is larger ***
***********************************************************************

Enter the first number (a): 10
Enter the second number (b): 5
a = 10, b = 5
a > b

Case 3: a < b

***********************************************************************
*** This program compare 2 numbers and tell you which one is larger ***
***********************************************************************

Enter the first number (a): 5
Enter the second number (b): 10
a = 5, b = 10
a < b

The condition check for all 3 cases work as expected.

Reference

Koenig, Andrew & Moo, Barbara E., Accelerated C++, Addison-Wesley, 2000