org.paukov.combinatorics3.PermutationWithRepetitionIterator Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of combinatoricslib3 Show documentation

Simple java library to generate permutations, combinations and other combinatorial sequences

There is a newer version: 3.4.0

package org.paukov.combinatorics3;


import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

class PermutationWithRepetitionIterator  implements Iterator> {

    final PermutationWithRepetitionGenerator _generator;

    List _currentPermutation = null;
    long _currentIndex = 0;

    final int _n;
    final int _k;

    // Internal data
    private int[] _bitVector = null;

    public PermutationWithRepetitionIterator(
            PermutationWithRepetitionGenerator generator) {
        _generator = generator;
        _n = generator._originalVector.size();
        _k = generator._permutationLength;

        List list = new ArrayList<>(_k);
        T defaultValue = generator._originalVector.get(0);
        for (int i = 0; i < _k; i++) {
            list.add(defaultValue);
        }

        _currentPermutation = new ArrayList<>(list);

        _bitVector = new int[_k + 2];
        for (int j = 0; j <= _k; j++) {
            _bitVector[j] = 0;
        }
        _currentIndex = 0;
    }


    @Override
    public boolean hasNext() {
        return (_bitVector[_k] != 1);
    }


    @Override
    public List next() {
        _currentIndex++;

        for (int j = _k - 1; j >= 0; j--) {
            _currentPermutation.set(j, _generator._originalVector.get(_bitVector[j]));
        }

        int i = 0;
        while (_bitVector[i] == _n - 1) {
            if (i < _k + 1)
                _bitVector[i] = 0;
            else {
                _bitVector[_k] = 1;
                return new ArrayList<>(_currentPermutation);
            }
            i++;
        }

        _bitVector[i]++;
        return new ArrayList<>(_currentPermutation);

    }

    @Override
    public void remove() {
        throw new UnsupportedOperationException();
    }


    @Override
    public String toString() {
        return "PermutationWithRepetitionIterator=[#" + _currentIndex + ", "
                + _currentPermutation + "]";
    }
}