Implementar rand3() usando rand2()
Dada una función rand2() que devuelve 0 o 1 con igual probabilidad, implemente rand3() usando rand2() que devuelve 0 1 o 2 con igual probabilidad. Minimiza el número de llamadas al método rand2(). Tampoco se permite el uso de ninguna otra función de biblioteca ni la aritmética de punto flotante.
La idea es utilizar la expresión. 2 * rand2() + rand2() . Devuelve 0 1 2 3 con igual probabilidad. Para que devuelva 0 1 2 con igual probabilidad eliminamos el evento no deseado 3.
A continuación se muestra la implementación de la idea anterior:
// C++ Program to print 0 1 or 2 with equal // probability #include using namespace std ; // Random Function to that returns 0 or 1 with // equal probability int rand2 () { // rand() function will generate odd or even // number with equal probability. If rand() // generates odd number the function will // return 1 else it will return 0. return rand () & 1 ; } // Random Function to that returns 0 1 or 2 with // equal probability 1 with 75% int rand3 () { // returns 0 1 2 or 3 with 25% probability int r = 2 * rand2 () + rand2 (); if ( r < 3 ) return r ; return rand3 (); } // Driver code to test above functions int main () { // Initialize random number generator srand ( time ( NULL )); for ( int i = 0 ; i < 100 ; i ++ ) cout < < rand3 (); return 0 ; }
Java // Java Program to print 0 1 or 2 with equal // probability import java.util.Random ; class GFG { // Random Function to that returns 0 or 1 with // equal probability static int rand2 () { // rand() function will generate odd or even // number with equal probability. If rand() // generates odd number the function will // return 1 else it will return 0. Random rand = new Random (); return ( rand . nextInt () & 1 ); } // Random Function to that returns 0 1 or 2 with // equal probability 1 with 75% static int rand3 () { // returns 0 1 2 or 3 with 25% probability int r = 2 * rand2 () + rand2 (); if ( r < 3 ) return r ; return rand3 (); } // Driver code public static void main ( String [] args ) { for ( int i = 0 ; i < 100 ; i ++ ) System . out . print ( rand3 ()); } } // This code is contributed by divyesh072019.
Python3 # Python3 Program to print 0 1 or 2 with equal # Probability import random # Random Function to that returns 0 or 1 with # equal probability def rand2 (): # randint(0100) function will generate odd or even # number [1100] with equal probability. If rand() # generates odd number the function will # return 1 else it will return 0 tmp = random . randint ( 1 100 ) return tmp % 2 # Random Function to that returns 0 1 or 2 with # equal probability 1 with 75% def rand3 (): # returns 0 1 2 or 3 with 25% probability r = 2 * rand2 () + rand2 () if r < 3 : return r return rand3 () # Driver code to test above functions if __name__ == '__main__' : for i in range ( 100 ): print ( rand3 () end = '' ) #This code is contributed by sahilshelangia
C# // C# Program to print 0 1 or 2 with equal // probability using System ; class GFG { // Random Function to that returns 0 or 1 with // equal probability static int rand2 () { // rand() function will generate odd or even // number with equal probability. If rand() // generates odd number the function will // return 1 else it will return 0. Random rand = new Random (); return ( rand . Next () & 1 ); } // Random Function to that returns 0 1 or 2 with // equal probability 1 with 75% static int rand3 () { // returns 0 1 2 or 3 with 25% probability int r = 2 * rand2 () + rand2 (); if ( r < 3 ) return r ; return rand3 (); } // Driver code static void Main () { for ( int i = 0 ; i < 100 ; i ++ ) Console . Write ( rand3 ()); } } // This code is contributed by divyeshrabadiya07.
PHP // PHP Program to print 0 1 or // 2 with equal probability // Random Function to that // returns 0 or 1 with // equal probability function rand2 () { // rand() function will generate // odd or even number with equal // probability. If rand() generates // odd number the function will // return 1 else it will return 0. return rand () & 1 ; } // Random Function to that // returns 0 1 or 2 with // equal probability 1 with 75% function rand3 () { // returns 0 1 2 or 3 // with 25% probability $r = 2 * rand2 () + rand2 (); if ( $r < 3 ) return $r ; return rand3 (); } // Driver Code // Initialize random // number generator srand ( time ( NULL )); for ( $i = 0 ; $i < 100 ; $i ++ ) echo rand3 (); // This code is contributed by aj_36 ?>
JavaScript < script > // Javascript program to print 0 1 or 2 with equal // probability // Random Function to that returns 0 or 1 with // equal probability function rand2 () { // Math.random()*2 function generates // 0 and 1 with equal probability return Math . floor ( Math . random () * 2 ); } // Random Function to that returns 0 1 or 2 with // equal probability 1 with 75% function rand3 () { // returns 0 1 2 or 3 with 25% probability var r = 2 * rand2 () + rand2 (); if ( r < 3 ) return r ; return rand3 (); } var ans = '' ; //to store the output for ( var i = 0 ; i < 100 ; i ++ ) ans += rand3 (); document . write ( ans ); // This code is contributed by shruti456rawal < /script>
Producción :
2111011101112002111002020210112022022022211100100121202021102100010200121121210122011022111020
Otra solución -
Si x = rand2() e y = rand2() x + y devolverá 0 y 2 con un 25% de probabilidad y 1 con un 50% de probabilidad. Para hacer que la probabilidad de 1 sea igual a la de 0 y 2, es decir, 25%, eliminamos un evento no deseado que resulta en x + y = 1, es decir, (x = 1 y = 0) o (x = 0 y = 1).
int rand3() { int x y; do { x = rand2(); y = rand2(); } while (x == 0 && y == 1); return x + y; }
Tenga en cuenta que las soluciones anteriores producirán resultados diferentes cada vez que las ejecutemos.
