COS126

• Download DiscreteDistribution.java

/*******************************************************************
 * Name:
 * Login:
 * Precept:
 *
 * Description: Reads in an array of N frequency counts from the
 * command line and prints out i with probability proportional to
 * the ith frequency count.
 *
 * Dependencies: None.
 *
 * Examples:
 * % java DiscreteDistribution 1 1 1 1 1 1     // six equally likely events
 * 3
 * % java DiscreteDistribution 1 1 1 1 1 1
 * 0
 * % java DiscreteDistribution 1 1 1 1 1 3     // six events, one 3x more 
 * 5                                           // likely than the others
 * % java DiscreteDistribution 1 1 1 1 1 3
 * 2
 * % java DiscreteDistribution 1 1 1 1 1 3
 * 5                                           Booksite Web Exercise 1.4.2
 *************************************************************************/

public class DiscreteDistribution {
    public static void main(String[] args) {

       // read in N frequencies.  store in integer array.
       int N = __________________________;
       ____________[] freq = __________ int[___];
       for (_____________________; __________________; __________) {
           freq[_____] = Integer.parseInt(__________________);
       }
     
       // compute total count of all frequencies
       int total = ______;
       for (int i = 0; i < N; i++) {
           total += __________________________________;
       }

       // generate random integer with probability proportional to frequency
       int r = (int) (total * Math.random());   // integer in [0, total)
       int sum = 0;
       int event = -1;
       for (int i = 0; i < N && sum <= r; i++) {
           sum += freq[i];
           event = i;
       }
         
       System.out.println(event);
    }
}