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C++ Exercises: Generate random integers in a specific range

C++ Numbers: Exercise-8 with Solution

Write a program in C++ to generate random integers in a specific range.

Pictorial Presentation:

C++ Exercises: Generate random integers in a specific range

Sample Solution:

C++ Code :

#include <cstdlib>
#include <ctime>
#include <iostream>

using namespace std;

int main() 
{
int ln,un;
 cout << "\n\n Generate random integer in a specific range: \n";
 cout << " --------------------------------------------------\n";
cout << " Input the lower range of number: ";
cin >> ln;
cout << " Input the upper range of number: ";
cin >> un;
     srand(time(NULL));
     cout<<" The random number between "<<ln<<" and "<<un<<" is: ";
cout <<  ln+rand() % static_cast<int>(un-ln+1) << endl;     
     return 0;

}

Sample Output:

Generate random integer in a specific range:                          
 --------------------------------------------------                    
 Input the lower range of number: 15                                   
 Input the upper range of number: 25                                   
 The random number between 15 and 25 is: 18 

Flowchart:

Flowchart: Generate random integers in a specific range

C++ Code Editor:

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Next: Write a program in C++ to check whether a given number is a Kaprekar number or not.

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C++ Programming: Tips of the Day

How to use the PI constant in C++?

On some (especially older) platforms (see the comments below) you might need to

#define _USE_MATH_DEFINES and then include the necessary header file:
#include<math.h>

and the value of pi can be accessed via:

M_PI

In math.h (2014) it is defined as:

# define M_PI           3.14159265358979323846  /* pi */

but check your math.h for more. An extract from the "old" math.h (in 2009):

/* Define _USE_MATH_DEFINES before including math.h to expose these macro
 * definitions for common math constants.  These are placed under an #ifdef 
 * since these commonly-defined names are not part of the C/C++ standards.
 */

However:

  1. on newer platforms (at least on my 64 bit Ubuntu 14.04) I do not need to define the _USE_MATH_DEFINES
  2. On (recent) Linux platforms there are long double values too provided as a GNU Extension:
# define M_PIl          3.14159265358979323846

Ref: https://bit.ly/3G4BgzQ