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Random Function

Explore how to create two overloaded random functions in C++. Understand the Linear Congruential Generator algorithm used for producing pseudo-random numbers, and implement these functions to generate both integer and ranged random values. This lesson provides insights into function overloading and random number generation techniques.

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Problem

Write a program that provides two overloaded random( ) functions. The first one generates an integer random number, whereas the second generates a random number that lies within the range passed to the random( ) function.

Coding solution

Here is a solution to the problem above.

C++
// Generation of random numbers using overloaded functions
#include <iostream>
int random ( int ) ;
int random ( int, int ) ;
int main( ) 
{
	int i, n ;
	
	std::cout << "Random numbers between 1 to 100: \n";
	for ( i = 0 ; i <= 9 ; i++ ) 
	{
		n = random ( 100 ) ;
		std::cout << n << "\n" ;
	}
	
	std::cout << "Random numbers between 100 to 500: \n";
	for ( i = 0 ; i <= 9 ; i++ ) 
	{
		n = random ( 100, 500 ) ;
		std::cout << n << "\n" ;
	}
}
int random ( int max ) 
{
	static int xn = time ( NULL ) % max ; 
	static int cons = time ( NULL ) % 100 ;
	static int mult = time ( NULL ) % 120 ;
	int xnplus1, temp ;
	
	xnplus1 = ( mult * xn + cons ) % max ;
	temp = xnplus1 ;
	xn = xnplus1 ;
	
	return ( temp ) ;
}
int random ( int min, int max ) 
{
	int range ;
	
	range = max - min ;
	
	static int xn = time ( NULL ) % range ; 
	static int cons = time ( NULL ) % 100 ;
	static int mult = time ( NULL ) % 120 ;
	int xnplus1, temp ;
	
	xnplus1 = ( mult * xn + cons ) % max ;
	temp = min + xnplus1 ;
	xn = xnplus1 ;
	
	return ( temp ) ;
}

Explanation

The program uses a Linear Congruential Generator (LCG) algorithm that yields a sequence of pseudo-random numbers calculated with a discontinuous piecewise linear equation. The generator is defined by the recurrence relation:

Xn+1=(a∗Xn+c)mod(m){X_{n+1} = ( a * X_{n} + c ) mod (m)} ...