de.tum.in.naturals.bitset.SparseBitSets Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of naturals-util Show documentation
Datastructures and utility classes for non-negative integers
The newest version!
/*
 * Copyright (C) 2017 Tobias Meggendorfer
 *
 * This program 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.
 *
 * This program 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 this program.  If not, see .
 */

package de.tum.in.naturals.bitset;

import com.zaxxer.sparsebits.SparseBitSet;
import de.tum.in.naturals.set.NatBitSet;
import de.tum.in.naturals.set.NatBitSets;
import it.unimi.dsi.fastutil.ints.IntIterable;
import it.unimi.dsi.fastutil.ints.IntIterator;
import it.unimi.dsi.fastutil.ints.IntSortedSet;
import java.util.BitSet;
import java.util.PrimitiveIterator;
import java.util.function.IntConsumer;
import javax.annotation.Nonnegative;

/**
 * Utility class to help interacting with {@link SparseBitSet}.
 */
public final class SparseBitSets {
    private SparseBitSets() {}

    public static SparseBitSet of() {
        return new SparseBitSet(0);
    }

    public static SparseBitSet of(int... indices) {
        SparseBitSet bitSet = new SparseBitSet();
        for (int index : indices) {
            bitSet.set(index);
        }
        return bitSet;
    }

    public static SparseBitSet of(IntIterable iterable) {
        if (iterable instanceof NatBitSet) {
            return NatBitSets.toSparseBitSet((NatBitSet) iterable);
        }

        SparseBitSet bitSet;
        if (iterable instanceof IntSortedSet) {
            IntSortedSet sortedSet = (IntSortedSet) iterable;
            if (sortedSet.comparator() == null) {
                bitSet = new SparseBitSet(sortedSet.lastInt() + 1);
            } else {
                bitSet = new SparseBitSet();
            }
        } else {
            bitSet = new SparseBitSet();
        }
        iterable.forEach((IntConsumer) bitSet::set);
        return bitSet;
    }

    public static SparseBitSet of(Iterable iterable) {
        if (iterable instanceof IntIterable) {
            return of((IntIterable) iterable);
        }

        SparseBitSet bitSet = new SparseBitSet();
        for (Integer integer : iterable) {
            bitSet.set(integer);
        }
        return bitSet;
    }

    @SuppressWarnings("TypeMayBeWeakened")
    public static SparseBitSet of(PrimitiveIterator.OfInt iterator) {
        SparseBitSet sparseBitSet = new SparseBitSet();
        iterator.forEachRemaining((IntConsumer) sparseBitSet::set);
        return sparseBitSet;
    }

    public static SparseBitSet of(BitSet bitSet) {
        SparseBitSet sparseBitSet = new SparseBitSet(bitSet.length());
        BitSets.forEach(bitSet, sparseBitSet::set);
        return sparseBitSet;
    }

    public static IntIterator complementIterator(SparseBitSet bitSet, int length) {
        return new SparseBitSetComplementIterator(bitSet, length);
    }

    public static void forEach(SparseBitSet bitSet, IntConsumer consumer) {
        int length = bitSet.length();
        int cardinality = bitSet.cardinality();
        if (length < cardinality * 2) {
            // the set is rather dense, meaning there probably are a lot of blocks of 1s
            int currentBlock = bitSet.nextSetBit(0);
            while (currentBlock > -1) {
                int blockEnd = bitSet.nextClearBit(currentBlock);
                assert blockEnd > currentBlock;
                for (int i = currentBlock; i < blockEnd; i++) {
                    consumer.accept(i);
                }
                currentBlock = bitSet.nextSetBit(blockEnd);
            }
        } else {
            for (int i = bitSet.nextSetBit(0); i >= 0; i = bitSet.nextSetBit(i + 1)) {
                consumer.accept(i);
            }
        }
    }

    /**
     * Checks if {@code first} is a subset of {@code second}.
     */
    public static boolean isSubset(SparseBitSet first, SparseBitSet second) {
        return isSubsetConsuming(first.clone(), second);
    }

    /**
     * Checks if {@code first} is a subset of {@code second}, potentially modifying both sets in the
     * process.
     */
    public static boolean isSubsetConsuming(SparseBitSet first, SparseBitSet second) {
        first.andNot(second);
        return first.isEmpty();
    }

    public static boolean isDisjoint(SparseBitSet first, SparseBitSet second) {
        return !first.intersects(second);
    }

    public static IntIterator iterator(SparseBitSet bitSet) {
        return new SparseBitSetIterator(bitSet);
    }

    public static int previousAbsentIndex(SparseBitSet set, @Nonnegative int index) {
        // Binary search for the biggest clear bit with index <= length
        if (!set.get(index)) {
            return index;
        }

        int firstAbsentIndex = set.nextClearBit(0);
        if (firstAbsentIndex > index) {
            return -1;
        }

        int high = index - 1;
        int low = firstAbsentIndex;

        while (true) {
            assert low <= high;
            int mid = (high + low) >>> 1;
            int next = set.nextClearBit(mid);
            while (next > index) {
                assert low <= mid && mid <= high;
                high = mid;
                mid = (high + low) >>> 1;
                next = set.nextClearBit(mid);
            }
            assert !set.get(next);
            low = next;
            int nextClear = set.nextClearBit(low + 1);
            if (nextClear > index) {
                return low;
            }
            low = nextClear;
        }
    }

    public static int previousPresentIndex(SparseBitSet set, @Nonnegative int index) {
        // Binary search for the biggest set bit with index <= length
        if (set.get(index)) {
            return index;
        }

        int firstPresentIndex = set.nextSetBit(0);
        if (firstPresentIndex == -1 || firstPresentIndex > index) {
            return -1;
        }

        int high = index - 1;
        int low = firstPresentIndex;

        while (true) {
            assert low <= high;
            int mid = (high + low) >>> 1;
            int next = set.nextSetBit(mid);
            while (next == -1 || next > index) {
                assert low <= mid && mid <= high;
                high = mid;
                mid = (high + low) >>> 1;
                next = set.nextSetBit(mid);
            }
            assert set.get(next);
            low = next;
            int nextSet = set.nextSetBit(low + 1);
            if (nextSet == -1 || nextSet > index) {
                return low;
            }
            low = nextSet;
        }
    }
}