src.it.unimi.dsi.fastutil.chars.CharHeaps 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) */
/* Equality */
/* Object/Reference-only definitions (keys) */
/* Primitive-type-only definitions (keys) */
/* Object/Reference-only definitions (values) */
/*
* 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.chars;
/** A class providing static methods and objects that do useful things with heaps.
*
* The static methods of this class allow to treat arrays as 0-based heaps. They
* are used in the implementation of heap-based queues, but they may be also used
* directly.
*
*/
public class CharHeaps {
private CharHeaps() {}
/** Moves the given element down into the heap until it reaches the lowest possible position.
*
* @param heap the heap (starting at 0).
* @param size the number of elements in the heap.
* @param i the index of the element that must be moved down.
* @param c a type-specific comparator, or null for the natural order.
* @return the new position of the element of index i.
*/
@SuppressWarnings("unchecked")
public static int downHeap( final char[] heap, final int size, int i, final CharComparator c ) {
if ( i >= size ) throw new IllegalArgumentException( "Heap position (" + i + ") is larger than or equal to heap size (" + size + ")" );
final char e = heap[ i ];
int child;
if ( c == null )
while ( ( child = 2 * i + 1 ) < size ) {
if ( child + 1 < size && ( (heap[ child + 1 ]) < (heap[ child ]) ) ) child++;
if ( ( (e) <= (heap[ child ]) ) ) break;
heap[ i ] = heap[ child ];
i = child;
}
else
while ( ( child = 2 * i + 1 ) < size ) {
if ( child + 1 < size && c.compare( heap[ child + 1 ], heap[ child ] ) < 0 ) child++;
if ( c.compare( e, heap[ child ] ) <= 0 ) break;
heap[ i ] = heap[ child ];
i = child;
}
heap[ i ] = e;
return i;
}
/** Moves the given element up in the heap until it reaches the highest possible position.
*
* @param heap the heap (starting at 0).
* @param size the number of elements in the heap.
* @param i the index of the element that must be moved up.
* @param c a type-specific comparator, or null for the natural order.
* @return the new position of the element of index i.
*/
@SuppressWarnings("unchecked")
public static int upHeap( final char[] heap, final int size, int i, final CharComparator c ) {
if ( i >= size ) throw new IllegalArgumentException( "Heap position (" + i + ") is larger than or equal to heap size (" + size + ")" );
final char e = heap[ i ];
int parent;
if ( c == null )
while ( i != 0 && ( parent = ( i - 1 ) / 2 ) >= 0 ) {
if ( ( (heap[ parent ]) <= (e) ) ) break;
heap[ i ] = heap[ parent ];
i = parent;
}
else
while ( i != 0 && ( parent = ( i - 1 ) / 2 ) >= 0 ) {
if ( c.compare( heap[ parent ], e ) <= 0 ) break;
heap[ i ] = heap[ parent ];
i = parent;
}
heap[ i ] = e;
return i;
}
/** Makes an array into a heap.
*
* @param heap the heap (starting at 0).
* @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 char[] heap, final int size, final CharComparator c ) {
int i = size / 2;
while( i-- != 0 ) downHeap( heap, size, i, c );
}
}