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/*
* Copyright (C) 2003-2015 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 PACKAGE;
#if #keyclass(Object)
import java.util.Comparator;
#endif
import java.util.Arrays;
/** 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 INDIRECT_HEAPS {
private INDIRECT_HEAPS() {}
/** 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.
*/
SUPPRESS_WARNINGS_KEY_UNCHECKED
public static KEY_GENERIC int downHeap( final KEY_GENERIC_TYPE[] refArray, final int[] heap, final int[] inv, final int size, int i, final KEY_COMPARATOR KEY_GENERIC c ) {
assert i < size;
final int e = heap[ i ];
final KEY_GENERIC_TYPE E = refArray[ e ];
int child;
if ( c == null )
while ( ( child = ( i << 1 ) + 1 ) < size ) {
int t = heap[ child ];
final int right = child + 1;
if ( right < size && KEY_LESS( refArray[ heap[ right ] ], refArray[ t ] ) ) t = heap[ child = right ];
if ( KEY_LESSEQ( E, refArray[ t ] ) ) break;
heap[ i ] = t;
inv[ heap[ i ] ] = i;
i = child;
}
else
while ( ( child = ( i << 1 ) + 1 ) < size ) {
int t = heap[ child ];
final int right = child + 1;
if ( right < size && c.compare( refArray[ heap[ right ] ], refArray[ t ] ) < 0 ) t = heap[ child = right ];
if ( c.compare( E, refArray[ t ] ) <= 0 ) break;
heap[ i ] = t;
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.
*/
SUPPRESS_WARNINGS_KEY_UNCHECKED
public static KEY_GENERIC int upHeap( final KEY_GENERIC_TYPE[] refArray, final int[] heap, final int[] inv, final int size, int i, final KEY_COMPARATOR KEY_GENERIC c ) {
assert i < size;
final int e = heap[ i ];
final KEY_GENERIC_TYPE E = refArray[ e ];
if ( c == null )
while ( i != 0 ) {
final int parent = ( i - 1 ) >>> 1;
final int t = heap[ parent ];
if ( KEY_LESSEQ( refArray[ t ], E ) ) break;
heap[ i ] = t;
inv[ heap[ i ] ] = i;
i = parent;
}
else
while ( i != 0 ) {
final int parent = ( i - 1 ) >>> 1;
final int t = heap[ parent ];
if ( c.compare( refArray[ t ], E ) <= 0 ) break;
heap[ i ] = t;
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 KEY_GENERIC void makeHeap( final KEY_GENERIC_TYPE[] refArray, final int offset, final int length, final int[] heap, final int[] inv, final KEY_COMPARATOR KEY_GENERIC c ) {
ARRAYS.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 + ")" );
Arrays.fill( inv, 0, refArray.length, -1 );
int i = length;
while( i-- != 0 ) inv[ heap[ i ] = offset + i ] = i;
i = length >>> 1;
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 KEY_GENERIC void makeHeap( final KEY_GENERIC_TYPE[] refArray, final int[] heap, final int[] inv, final int size, final KEY_COMPARATOR KEY_GENERIC c ) {
int i = size >>> 1;
while( i-- != 0 ) downHeap( refArray, heap, inv, size, i, c );
}
}