This document contains 5 problems and solutions related to writing C++ programs. Problem 1 asks to write a program that repeatedly collects positive integers from the user until a negative number is entered, then outputs the product of the positive numbers. Problem 2 asks to write a program that counts the even and odd numbers entered by the user until a negative number is entered. Problem 3 asks to output all divisors of a number entered by the user in ascending order. Problem 4 asks to output the two largest numbers from a list of numbers entered by the user until a negative number is entered. Problem 5 asks to convert a number of seconds after midnight to hours:minutes:seconds format. Solutions in C++ are provided for each problem.

1. Introduction to Computers
Lab 11
First Year (2016– 2017)
Introduction to Computers Lab First Year 2016– 2017

2. Problem 1
• Write a program that repeatedly collects positive
integers from the user, stopping when the user enters
a negative number or zero. After that, output the
product of all positive entries.
• A sample run should appear on the screen like the text
below.
Enter a number: 3
Enter a number: 10
Enter a number: 2
Enter a number: -13
The product of all your positive numbers is 60.
2

3. Solution
#include <iostream>
using namespace std;
int main( )
{
int x = 1;
int product = 1;
while ( x > 0 )
{
product *= x;
cout << "Enter a number: ";
cin >> x;
}
cout << "The product of all your positive numbers
is " << product << endl;
return 0;
} 3

4. Another Solution:
using break
4
#include <iostream>
using namespace std;
int main( )
{
int x = 1, product = 1;
while (true)
{
cout << "Enter a number: ";
cin >> x;
if (x <= 0)
break;
product *= x;
}
cout << "The product of all your positive numbers is " <<
product << endl;
return 0;
}

5. Problem 2
• Write a program that accepts from the user a list of
positive integers and displays the number of even and
odd values in the list. The program accepts numbers
from the user until he enters a negative value.
• A sample run of the previous program is given below:
Enter the numbers:
1
6
3
4
8
-1
The number of even values = 3
The number of odd values = 2
5

6. 6
#include <iostream>
using namespace std;
int main()
{
int x;
int odd=0, even=0;
cout<<"Enter positive numbers (negative number to terminate):"<<endl;
while(true)
{
cin>>x;
if(x<0)
break;
else
{
if(x%2==0)
even++;
else
odd++;
}
}
cout<<"Even Numbers= "<< even <<endl;
cout<<"Odd numbers= "<< odd <<endl;
return 0;
}
Solution

7. Problem 3
• Write a program that asks the user to enter an integer
and reports all divisors in ascending order.
• An example is shown below, where the user entered
30.
Enter a number: 30
The divisors are: 1 2 3 5 6 10 15 30
7

8. Solution
#include <iostream>
using namespace std;
int main()
{
cout << "Enter a number: ";
int num;
cin >> num;
cout << "The divisors are: ";
for (int i=1; i<=num; i++)
{
if (num%i == 0)
cout << i << " ";
}
return 0;
}
8

9. Problem 4
• Write a program that accepts numbers from the user
and then tells the maximum two numbers of them.
The results should be displayed when the user
enters a negative number.
• A sample run of the program should be like:
Enter numbers (less than 0 to end): 5
33
7
53
52
14
12
45
-1
The maximum two numbers are 53 and 52.
9

10. int main()
{
int x, max_Num1=0, max_Num2=0;
cout<<"Enter numbers (less than 0 to end): "<<endl;
while (true)
{
cin>> x;
if(x<0)
break;
else
{
if(x<max_Num1)
{
if(x>max_Num2)
max_Num2=x;
}
else
{
max_Num2=max_Num1;
max_Num1=x;
}
}
}
cout<<"Max 1= "<<max_Num1<<endl;
cout<<"Max 2= "<<max_Num2<<endl;
return 0;
} 10
Solution

11. Problem 5
• Write a program that takes as input the number of
seconds after midnight. It then displays the time in
hours:minutes:seconds format.
• Your program should show output as in the example
below.
Enter number of seconds after midnight: 3601
The time is 01:00:01
11

12. Solution
#include <iostream>
using namespace std;
int main( )
{
int seconds;
cout << "Enter number of seconds after midnight: ";
cin >> seconds;
int hours = seconds / 3600;
int mins = (seconds-hours*3600)/60;
int secs = (seconds-hours*3600)%60;
cout << "The time is ";
if (hours < 10)
cout << "0";
cout << hours << ":";
if (mins < 10)
cout << "0";
cout << mins << ":";
if (secs < 10)
cout << "0";
cout << secs << "n";
return 0;
} 12

13. Thank you 