C++ Programming Code Examples
C++ > Data Structures and Algorithm Analysis in C++ Code Examples
Implementation for random number class
/* Implementation for random number class */
#include "Random.h"
static const int A = 48271;
static const int M = 2147483647;
static const int Q = M / A;
static const int R = M % A;
/**
* Construct with initialValue for the state.
*/
Random::Random( int initialValue )
{
if( initialValue < 0 )
initialValue += M;
state = initialValue;
if( state == 0 )
state = 1;
}
/**
* Return a pseudorandom int, and change the
* internal state.
*/
int Random::randomInt( )
{
int tmpState = A * ( state % Q ) - R * ( state / Q );
if( tmpState >= 0 )
state = tmpState;
else
state = tmpState + M;
return state;
}
/**
* Return a pseudorandom int, and change the
* internal state. DOES NOT WORK.
*/
int Random::randomIntWRONG( )
{
return state = ( A * state ) % M;
}
/**
* Return a pseudorandom double in the open range 0..1
* and change the internal state.
*/
double Random::random0_1( )
{
return (double) randomInt( ) / M;
}
/**
* Return an int in the closed range [low,high], and
* change the internal state.
*/
int Random::randomInt( int low, int high )
{
double partitionSize = (double) M / ( high - low + 1 );
return (int) ( randomInt( ) / partitionSize ) + low;
}
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