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/* 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) 2003-2015 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 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. */
public static int downHeap( final char[] heap, final int size, int i, final CharComparator c ) {
assert i < size;
final char e = heap[ i ];
int child;
if ( c == null ) while ( ( child = ( i << 1 ) + 1 ) < size ) {
char t = heap[ child ];
final int right = child + 1;
if ( right < size && ( ( heap[ right ] ) < ( t ) ) ) t = heap[ child = right ];
if ( ( ( e ) <= ( t ) ) ) break;
heap[ i ] = t;
i = child;
}
else while ( ( child = ( i << 1 ) + 1 ) < size ) {
char t = heap[ child ];
final int right = child + 1;
if ( right < size && c.compare( heap[ right ], t ) < 0 ) t = heap[ child = right ];
if ( c.compare( e, t ) <= 0 ) break;
heap[ i ] = t;
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. */
public static int upHeap( final char[] heap, final int size, int i, final CharComparator c ) {
assert i < size;
final char e = heap[ i ];
if ( c == null ) while ( i != 0 ) {
final int parent = ( i - 1 ) >>> 1;
final char t = heap[ parent ];
if ( ( ( t ) <= ( e ) ) ) break;
heap[ i ] = t;
i = parent;
}
else while ( i != 0 ) {
final int parent = ( i - 1 ) >>> 1;
final char t = heap[ parent ];
if ( c.compare( t, e ) <= 0 ) break;
heap[ i ] = t;
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 >>> 1;
while ( i-- != 0 )
downHeap( heap, size, i, c );
}
}