edu.asu.ca.kaushik.algorithms.structures.ColGrIterator2.java Source code

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Here is the source code for edu.asu.ca.kaushik.algorithms.structures.ColGrIterator2.java

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/**
 * Copyright (C) 2013-2016 Kaushik Sarkar <ksarkar1@asu.edu>
 * 
 * This file is part of CoveringArray project.
 * 
 * CoveringArray is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the 
 * Free Software Foundation, either version 3 of the License, or (at your option) any later version.
 * 
 * CoveringArray is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 
 * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License along with CoveringArray.  If not, see <http://www.gnu.org/licenses/>.
 */

package edu.asu.ca.kaushik.algorithms.structures;

import java.util.Date;

import org.apache.commons.math3.util.CombinatoricsUtils;

public class ColGrIterator2 implements ColGrIterator {
    long numGroups;
    long count;
    int[] cols;
    int t;
    int k;

    /**
     * Memory efficient ColGrIterator. Generates the column groups on the fly.
     * Hence does not require huge memory. But takes a lot of time.
     * @param t
     * @param k
     */
    public ColGrIterator2(int t, int k) {
        assert (t <= k);

        this.t = t;
        this.k = k;
        this.numGroups = (long) CombinatoricsUtils.binomialCoefficientDouble(k, t);
        this.count = 1;
        this.cols = new int[t];
        this.initiateCols();
    }

    private void initiateCols() {
        for (int i = 0; i < this.t; i++) {
            this.cols[i] = i;
        }
        this.cols[this.t - 1]--;
    }

    @Override
    public boolean hasNext() {
        return (this.count <= this.numGroups) ? true : false;
    }

    @Override
    public ColGroup next() {
        do {
            this.incrementCounter();
        } while (!this.validCombination());

        this.count++;
        return new ColGroup(this.cols);
    }

    private void incrementCounter() {
        int ind = t - 1;
        while (this.cols[ind] == this.k - 1) {
            this.cols[ind] = 0;
            ind--;
        }
        this.cols[ind]++;
    }

    private boolean validCombination() {
        for (int i = 0; i < this.t; i++) {
            for (int j = i - 1; j >= 0; j--) {
                if (this.cols[i] <= this.cols[j]) {
                    return false;
                }
            }
        }
        return true;
    }

    @Override
    public void rewind() {
        this.count = 1;
        this.initiateCols();
    }

    /**
     * @param args
     */
    public static void main(String[] args) {
        int t = 6;
        int k = 52;

        System.out.println("Time efficient:");
        System.out.println(new Date());
        ColGrIterator ci = new ColGrIterator1(t, k);
        long tot = 0;
        while (ci.hasNext()) {
            //System.out.println(ci.next());
            ci.next();
            tot++;
        }
        System.out.println(new Date());
        System.out.println("total = " + tot);

        System.out.println();

        System.out.println("Memory efficient:");
        System.out.println(new Date());
        ci = new ColGrIterator2(t, k);
        tot = 0;
        while (ci.hasNext()) {
            //System.out.println(ci.next());
            ci.next();
            tot++;
        }
        System.out.println(new Date());
        System.out.println("total = " + tot);

    }

}