StableMatching.java

import java.util.HashSet;

public class StableMatching {

	public static class Person
	{
		Person[] preferences;
		int id = -1;
		boolean isEngaged = false;
		Person engagedTo = null;
		int lastProposedToIndex = -1;
		int currentlyEngagedIndex = -1;
	}
	
	static Person[] allMen;
	static Person[] allWomen;
	
	public static void initPersons(Person[] persons)
	{
		for (int i = 0; i < persons.length; i++)
		{
			persons[i] = new Person();
			persons[i].id = i;
			persons[i].preferences = new Person[persons.length];
		}
	}	
	
	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		int numTries[] = {4,10,20,50,70,100,150,300,500,600,700};//1000};
		double n = 3;
		for (int i = 1; i < numTries.length; i++)
		{
			int M=0;
			int W=0;
			int numSamples = numTries[i];
			double numSamplesFloat = 1.0*numSamples;
			for (int j=0; j<n; j++){
				generateRandomLists(numSamples);
				generateStableMatching(numSamples);
				for (int k = 0; k < numSamples; k++)
				{
					M += allMen[k].lastProposedToIndex+1;
					W += allWomen[k].currentlyEngagedIndex+1;
				}
			}
			String s = String.format("%d,M,%f,W,%f", numSamples,(double) (M/numSamplesFloat), (double) W/numSamplesFloat);
			System.out.println(s);
		}
		System.out.println("okay done...");
	}
	
	private static void printOutMatchingIndexes(int n) {
		int M=0;
		int N=0;
		for (int i = 0; i < n; i++)
		{
			M += allMen[i].lastProposedToIndex+1;
			N += allWomen[i].currentlyEngagedIndex+1;
			String s = String.format("M,%d,W,%d", allMen[i].lastProposedToIndex+1, allWomen[i].currentlyEngagedIndex);
			//System.out.println(s);
		}
		System.out.println("Final Ranks" + M + ":" + N);
		
	}

	public static void generateStableMatching(int n)
	{
		// list of men and their preferences
		int numEngaged = 0;
		while (numEngaged != n)
		{
			
			//System.out.println("number left" + numEngaged);
			for (int i=0; i < n; i++)
			{
				Person currMan = allMen[i];
				if (!currMan.isEngaged)
				{
					int currIndexToPropose = currMan.lastProposedToIndex+1;
					Person currWoman = currMan.preferences[currIndexToPropose];
					if (!currWoman.isEngaged)
					{
						// engage the man and woman
						currMan.isEngaged = true;
						currWoman.isEngaged = true;
						currWoman.currentlyEngagedIndex = findIndexOfMan(currWoman, currMan.id);
						numEngaged++;
					}
					else
					{
						int manIndex = findIndexOfMan(currWoman, currMan.id);
						if (manIndex < currWoman.currentlyEngagedIndex)
						{
							currWoman.preferences[currWoman.currentlyEngagedIndex].isEngaged = false;
							currWoman.currentlyEngagedIndex = manIndex;
							currWoman.isEngaged = true;
							currMan.isEngaged = true;
							
						}
					}
					currMan.lastProposedToIndex++;
				}
			}
		}
		
		
	}
	
	private static int findIndexOfMan(Person currWoman, int id) {
		for (int i = 0 ; i < currWoman.preferences.length; i++)
		{
			Person currMan = currWoman.preferences[i];
			if (currMan.id == id)
			{
				return i;
			}
		}
		return 0;
	}

	public static void generateRandomLists(int n)
	{
		// each man will have a random list of women

		allMen = new Person[n];
		allWomen = new Person[n];
		//System.out.println("starting generation");
		initPersons(allMen);
		initPersons(allWomen);
		
		for (int i=0; i < n; i++)
		{
			HashSet<Integer> indexesUsed = new HashSet<Integer>(n);
			//System.out.println(i);
			for (int j=0; j < n; j++)
			{
				int indexToUse = (int) (Math.random() * 1.0 * n);
				while (indexesUsed.contains(indexToUse))
				{
					indexToUse = (int) (Math.random() * 1.0 * n);
				}
				allMen[i].preferences[j] = allWomen[indexToUse];
				indexesUsed.add(indexToUse);
			}
			if (indexesUsed.size() != n)
			{
				System.out.println("woops. not fully specifying preference list");
			}
		}
		
		for (int i=0; i < n; i++)
		{
			HashSet<Integer> indexesUsed = new HashSet<Integer>(n);
			for (int j=0; j < n; j++)
			{
				int indexToUse = (int) (Math.random() * 1.0 * n);
				while (indexesUsed.contains(indexToUse))
				{
					indexToUse = (int) (Math.random() * 1.0 * n);
				}
				allWomen[i].preferences[j] = allMen[indexToUse];
				indexesUsed.add(indexToUse);
			}
			if (indexesUsed.size() != n)
			{
				System.out.println("woops. not fully specifying preference list");
			}
		}
		
	}

}