package math;

/**

* Create a random number generator with equal probability from 1 to 7 using a

* random number generator that gives number from 1 to 5.

*

* Link: http://www.geeksforgeeks.org/generate-integer-from-1-to-7-with-equal-

* probability/

*

* @author shivam.maharshi

*/

public class Rand7FromRand5 {

public static int rand_7() {

int[][] vals = {

{ 1, 2, 3, 4, 5 },

{ 6, 7, 1, 2, 3 },

{ 4, 5, 6, 7, 1 },

{ 2, 3, 4, 5, 6 },

{ 7, 0, 0, 0, 0 }

};

int result = 0;

while (result == 0)

{

int i = rand5();

int j = rand5();

result = vals[i-1][j-1];

}

return result;

}

public static int rand7() {

int n = 5 * rand5() + rand5() - 5;

while (n > 21) {

n += 5 * rand5() + rand5() - 5;

}

return n % 7 + 1;

}

private static int rand5() {

return (int) (5 * Math.random()) + 1;

}

public static void main(String[] args) {

System.out.println(rand7());

System.out.println(rand_7());

}

}