DiscreteDistribution.java

Below is the syntax highlighted version of DiscreteDistribution.java.

/*******************************************************************
 *  Login, etc:
 *  Compile: javac DiscreteDistribution.java
 *  Execute: java DiscreteDistribution freq0 freq1 freq2 . . .
 *
 *  Reads in an array of N frequency counts from the command line,
 *  and prints out i with probability proportional to the ith
 *  frequency count.
 *
 *  // six equally likely events
 *  % java DiscreteDistribution 1 1 1 1 1 1
 *  3
 *
 *  % java DiscreteDistribution 1 1 1 1 1 1
 *  0
 *
 *  // six events, one 3x more likely than the others
 *  % java DiscreteDistribution 1 1 1 1 1 3
 *  5
 *
 *  % java DiscreteDistribution 1 1 1 1 1 3
 *  2
 *
 *  % java DiscreteDistribution 1 1 1 1 1 3
 *  5
 *************************************************************************/

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);
    }
}