import java.util.*;

public class ShortestQueue {

    public static void main (String[] argv)
    {
        // Four experiments with random-Queue using 100,1000,10000 and 100,000 customers.
	randomQueue (100, 1, 0.6, 0.6);
	randomQueue (1000, 1, 0.6, 0.6);
	randomQueue (10000, 1, 0.6, 0.6);
	randomQueue (100000, 1, 0.6, 0.6);

        // Four experiments with shortest-Queue using 100,1000,10000 and 100,000 customers.
	shortestQueue (100, 1, 0.6, 0.6);
	shortestQueue (1000, 1, 0.6, 0.6);
	shortestQueue (10000, 1, 0.6, 0.6);
	shortestQueue (100000, 1, 0.6, 0.6);
    }



    static void randomQueue (int numTimeSteps, double arrivalRate, double server1Rate, double server2Rate)
    {
        // Create two queues.
	LinkedList<Integer> queue1 = new LinkedList<Integer>();
	LinkedList<Integer> queue2 = new LinkedList<Integer>();

        // Statistics that we'll track.
	double sumOfWaitTimes = 0;
	int numCustServed = 0;

        // Repeat for numTimeSteps steps.

	for (int n=0; n<numTimeSteps; n++) {

	    // See if arrival occurs and if so, which queue it should join.
	    if (UniformRandom.uniform() < arrivalRate) {
		// Now choose a queue randomly (flip a coin).
		if (UniformRandom.uniform() > 0.5) {
                    // We'll store the time-stamp for each customer.
		    queue1.add (n); 
		}
		else {
		    queue2.add (n);
		}
	    }

	    // See if anyone completes in queue 1.
	    if ( (! queue1.isEmpty()) && 
		 (UniformRandom.uniform() < server1Rate) ) {
		int arrivalTime = queue1.remove();
		sumOfWaitTimes += (n - arrivalTime);
		numCustServed ++;
	    }	    

	    // See if anyone completes in queue 2.
	    if ( (! queue2.isEmpty()) && 
		 (UniformRandom.uniform() < server2Rate) ) {
		int arrivalTime = queue2.remove();
		sumOfWaitTimes += (n - arrivalTime);
		numCustServed ++;
	    }	    

	} //end-for

	double avgWaitTime = sumOfWaitTimes / numCustServed;
	System.out.println ("Random queue stats:#time steps=" + numTimeSteps);
	System.out.println ("  Average wait time: " + avgWaitTime);
	System.out.println ("  Num left in system: " + (queue1.size() + queue2.size()) );
    }



    static void shortestQueue (int numTimeSteps, double arrivalRate, double server1Rate, double server2Rate)
    {
        // Create the two queues.
	LinkedList<Integer> queue1 = new LinkedList<Integer>();
	LinkedList<Integer> queue2 = new LinkedList<Integer>();

        // Stats.
	double sumOfWaitTimes = 0;
	int numCustServed = 0;

        // Repeat for given number of time steps.
	for (int n=0; n<numTimeSteps; n++) {

	    // See if arrival occurs.
	    if (UniformRandom.uniform() < arrivalRate) {
		// Now choose shortest queue.
		if (queue1.size() > queue2.size()) {
		    queue2.add (n);
		}
		else {
		    queue1.add (n);
		}
	    }

	    // See if anyone completes in queue 1.
	    if ( (! queue1.isEmpty()) && 
		 (UniformRandom.uniform() < server1Rate) ) {
		int arrivalTime = queue1.remove();
		sumOfWaitTimes += (n - arrivalTime);
		numCustServed ++;
	    }	    

	    // See if anyone completes in queue 2.
	    if ( (! queue2.isEmpty()) && 
		 (UniformRandom.uniform() < server2Rate) ) {
		int arrivalTime = queue2.remove();
		sumOfWaitTimes += (n - arrivalTime);
		numCustServed ++;
	    }	    
	} //end-for

	double avgWaitTime = sumOfWaitTimes / numCustServed;
	System.out.println ("Shortest queue stats:#time steps=" + numTimeSteps);
	System.out.println ("  Average wait time: " + avgWaitTime);
	System.out.println ("  Num left in system: " + (queue1.size() + queue2.size()) );
    }

}