src.it.unimi.dsi.fastutil.bytes.ByteIndirectHeaps Maven / Gradle / Ivy
/* Generic definitions */
/* Assertions (useful to generate conditional code) */
/* Current type and class (and size, if applicable) */
/* Value methods */
/* Interfaces (keys) */
/* Interfaces (values) */
/* Abstract implementations (keys) */
/* Abstract implementations (values) */
/* Static containers (keys) */
/* Static containers (values) */
/* Implementations */
/* Synchronized wrappers */
/* Unmodifiable wrappers */
/* Other wrappers */
/* Methods (keys) */
/* Methods (values) */
/* Methods (keys/values) */
/* Methods that have special names depending on keys (but the special names depend on values) */
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/*
* Copyright (C) 2003-2013 Paolo Boldi and Sebastiano Vigna
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package it.unimi.dsi.fastutil.bytes;
import it.unimi.dsi.fastutil.ints.IntArrays;
/** A class providing static methods and objects that do useful things with indirect heaps.
*
* An indirect heap is an extension of a semi-indirect heap using also an
* inversion array of the same length as the reference array,
* satisfying the relation heap[inv[i]]==i when
* inv[i]>=0, and inv[heap[i]]==i for all elements in the heap.
*/
public class ByteIndirectHeaps {
private ByteIndirectHeaps() {}
/** Moves the given element down into the indirect heap until it reaches the lowest possible position.
*
* @param refArray the reference array.
* @param heap the indirect heap (starting at 0).
* @param inv the inversion array.
* @param size the number of elements in the heap.
* @param i the index in the heap of the element to be moved down.
* @param c a type-specific comparator, or null for the natural order.
* @return the new position in the heap of the element of heap index i.
*/
@SuppressWarnings("unchecked")
public static int downHeap( final byte[] refArray, final int[] heap, final int[] inv, final int size, int i, final ByteComparator c ) {
if ( i >= size ) throw new IllegalArgumentException( "Heap position (" + i + ") is larger than or equal to heap size (" + size + ")" );
final int e = heap[ i ];
final byte E = refArray[ e ];
int child;
if ( c == null )
while ( ( child = 2 * i + 1 ) < size ) {
if ( child + 1 < size && ( (refArray[ heap[ child + 1 ] ]) < (refArray[ heap[ child ] ]) ) ) child++;
if ( ( (E) <= (refArray[ heap[ child ] ]) ) ) break;
heap[ i ] = heap[ child ];
inv[ heap[ i ] ] = i;
i = child;
}
else
while ( ( child = 2 * i + 1 ) < size ) {
if ( child + 1 < size && c.compare( refArray[ heap[ child + 1 ] ], refArray[ heap[ child ] ] ) < 0 ) child++;
if ( c.compare( E, refArray[ heap[ child ] ] ) <= 0 ) break;
heap[ i ] = heap[ child ];
inv[ heap[ i ] ] = i;
i = child;
}
heap[ i ] = e;
inv[ e ] = i;
return i;
}
/** Moves the given element up in the indirect heap until it reaches the highest possible position.
*
* Note that in principle after this call the heap property may be violated.
*
* @param refArray the reference array.
* @param heap the indirect heap (starting at 0).
* @param inv the inversion array.
* @param size the number of elements in the heap.
* @param i the index in the heap of the element to be moved up.
* @param c a type-specific comparator, or null for the natural order.
* @return the new position in the heap of the element of heap index i.
*/
@SuppressWarnings("unchecked")
public static int upHeap( final byte[] refArray, final int[] heap, final int[] inv, final int size, int i, final ByteComparator c ) {
if ( i >= size ) throw new IllegalArgumentException( "Heap position (" + i + ") is larger than or equal to heap size (" + size + ")" );
final int e = heap[ i ];
final byte E = refArray[ e ];
int parent;
if ( c == null )
while ( i != 0 && ( parent = ( i - 1 ) / 2 ) >= 0 ) {
if ( ( (refArray[ heap[ parent ] ]) <= (E) ) ) break;
heap[ i ] = heap[ parent ];
inv[ heap[ i ] ] = i;
i = parent;
}
else
while ( i != 0 && ( parent = ( i - 1 ) / 2 ) >= 0 ) {
if ( c.compare( refArray[ heap[ parent ] ], E ) <= 0 ) break;
heap[ i ] = heap[ parent ];
inv[ heap[ i ] ] = i;
i = parent;
}
heap[ i ] = e;
inv[ e ] = i;
return i;
}
/** Creates an indirect heap in the given array.
*
* @param refArray the reference array.
* @param offset the first element of the reference array to be put in the heap.
* @param length the number of elements to be put in the heap.
* @param heap the array where the heap is to be created.
* @param inv the inversion array.
* @param c a type-specific comparator, or null for the natural order.
*/
public static void makeHeap( final byte[] refArray, final int offset, final int length, final int[] heap, final int[] inv, final ByteComparator c ) {
ByteArrays.ensureOffsetLength( refArray, offset, length );
if ( heap.length < length ) throw new IllegalArgumentException( "The heap length (" + heap.length + ") is smaller than the number of elements (" + length + ")" );
if ( inv.length < refArray.length ) throw new IllegalArgumentException( "The inversion array length (" + heap.length + ") is smaller than the length of the reference array (" + refArray.length + ")" );
IntArrays.fill( inv, 0, refArray.length, -1 );
int i = length;
while( i-- != 0 ) inv[ heap[ i ] = offset + i ] = i;
i = length / 2;
while( i-- != 0 ) downHeap( refArray, heap, inv, length, i, c );
}
/** Creates an indirect heap from a given index array.
*
* @param refArray the reference array.
* @param heap an array containing indices into refArray.
* @param inv the inversion array.
* @param size the number of elements in the heap.
* @param c a type-specific comparator, or null for the natural order.
*/
public static void makeHeap( final byte[] refArray, final int[] heap, final int[] inv, final int size, final ByteComparator c ) {
int i = size / 2;
while( i-- != 0 ) downHeap( refArray, heap, inv, size, i, c );
}
}