src.it.unimi.dsi.fastutil.objects.ObjectArrays 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) */
/* Object/Reference-only definitions (values) */
/*
* Copyright (C) 2002-2013 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.
*
*
*
* For the sorting and binary search code:
*
* Copyright (C) 1999 CERN - European Organization for Nuclear Research.
*
* Permission to use, copy, modify, distribute and sell this software and
* its documentation for any purpose is hereby granted without fee,
* provided that the above copyright notice appear in all copies and that
* both that copyright notice and this permission notice appear in
* supporting documentation. CERN makes no representations about the
* suitability of this software for any purpose. It is provided "as is"
* without expressed or implied warranty.
*/
package it.unimi.dsi.fastutil.objects;
import it.unimi.dsi.fastutil.Arrays;
import it.unimi.dsi.fastutil.Hash;
import java.util.Random;
import java.util.Comparator;
/** A class providing static methods and objects that do useful things with type-specific arrays.
*
* In particular, the ensureCapacity(), grow(),
* trim() and setLength() methods allow to handle
* arrays much like array lists. This can be very useful when efficiency (or
* syntactic simplicity) reasons make array lists unsuitable.
*
* Warning: creating arrays
* using {@linkplain java.lang.reflect.Array#newInstance(Class,int) reflection}, as it
* happens in {@link #ensureCapacity(Object[],int,int)} and {@link #grow(Object[],int,int)},
* is significantly slower than using new. This phenomenon is particularly
* evident in the first growth phases of an array reallocated with doubling (or similar) logic.
*
* @see java.util.Arrays
*/
public class ObjectArrays {
private ObjectArrays() {}
/** A static, final, empty array. */
public final static Object[] EMPTY_ARRAY = {};
/** Creates a new array using a the given one as prototype.
*
*
This method returns a new array of the given length whose element
* are of the same class as of those of prototype. In case
* of an empty array, it tries to return {@link #EMPTY_ARRAY}, if possible.
*
* @param prototype an array that will be used to type the new one.
* @param length the length of the new array.
* @return a new array of given type and length.
*/
@SuppressWarnings("unchecked")
private static K[] newArray( final K[] prototype, final int length ) {
final Class componentType = prototype.getClass().getComponentType();
if ( length == 0 && componentType == Object.class ) return (K[])EMPTY_ARRAY;
return (K[])java.lang.reflect.Array.newInstance( prototype.getClass().getComponentType(), length );
}
/** Ensures that an array can contain the given number of entries.
*
* If you cannot foresee whether this array will need again to be
* enlarged, you should probably use grow() instead.
*
* @param array an array.
* @param length the new minimum length for this array.
* @return array, if it contains length entries or more; otherwise,
* an array with length entries whose first array.length
* entries are the same as those of array.
*/
public static K[] ensureCapacity( final K[] array, final int length ) {
if ( length > array.length ) {
final K t[] =
newArray( array, length );
System.arraycopy( array, 0, t, 0, array.length );
return t;
}
return array;
}
/** Ensures that an array can contain the given number of entries, preserving just a part of the array.
*
* @param array an array.
* @param length the new minimum length for this array.
* @param preserve the number of elements of the array that must be preserved in case a new allocation is necessary.
* @return array, if it can contain length entries or more; otherwise,
* an array with length entries whose first preserve
* entries are the same as those of array.
*/
public static K[] ensureCapacity( final K[] array, final int length, final int preserve ) {
if ( length > array.length ) {
final K t[] =
newArray( array, length );
System.arraycopy( array, 0, t, 0, preserve );
return t;
}
return array;
}
/** Grows the given array to the maximum between the given length and
* the current length multiplied by two, provided that the given
* length is larger than the current length.
*
* If you want complete control on the array growth, you
* should probably use ensureCapacity() instead.
*
* @param array an array.
* @param length the new minimum length for this array.
* @return array, if it can contain length
* entries; otherwise, an array with
* max(length,array.length/φ) entries whose first
* array.length entries are the same as those of array.
* */
public static K[] grow( final K[] array, final int length ) {
if ( length > array.length ) {
final int newLength = (int)Math.min( Math.max( 2L * array.length, length ), Arrays.MAX_ARRAY_SIZE );
final K t[] =
newArray( array, newLength );
System.arraycopy( array, 0, t, 0, array.length );
return t;
}
return array;
}
/** Grows the given array to the maximum between the given length and
* the current length multiplied by two, provided that the given
* length is larger than the current length, preserving just a part of the array.
*
* If you want complete control on the array growth, you
* should probably use ensureCapacity() instead.
*
* @param array an array.
* @param length the new minimum length for this array.
* @param preserve the number of elements of the array that must be preserved in case a new allocation is necessary.
* @return array, if it can contain length
* entries; otherwise, an array with
* max(length,array.length/φ) entries whose first
* preserve entries are the same as those of array.
* */
public static K[] grow( final K[] array, final int length, final int preserve ) {
if ( length > array.length ) {
final int newLength = (int)Math.min( Math.max( 2L * array.length, length ), Arrays.MAX_ARRAY_SIZE );
final K t[] =
newArray( array, newLength );
System.arraycopy( array, 0, t, 0, preserve );
return t;
}
return array;
}
/** Trims the given array to the given length.
*
* @param array an array.
* @param length the new maximum length for the array.
* @return array, if it contains length
* entries or less; otherwise, an array with
* length entries whose entries are the same as
* the first length entries of array.
*
*/
public static K[] trim( final K[] array, final int length ) {
if ( length >= array.length ) return array;
final K t[] =
newArray( array, length );
System.arraycopy( array, 0, t, 0, length );
return t;
}
/** Sets the length of the given array.
*
* @param array an array.
* @param length the new length for the array.
* @return array, if it contains exactly length
* entries; otherwise, if it contains more than
* length entries, an array with length entries
* whose entries are the same as the first length entries of
* array; otherwise, an array with length entries
* whose first array.length entries are the same as those of
* array.
*
*/
public static K[] setLength( final K[] array, final int length ) {
if ( length == array.length ) return array;
if ( length < array.length ) return trim( array, length );
return ensureCapacity( array, length );
}
/** Returns a copy of a portion of an array.
*
* @param array an array.
* @param offset the first element to copy.
* @param length the number of elements to copy.
* @return a new array containing length elements of array starting at offset.
*/
public static K[] copy( final K[] array, final int offset, final int length ) {
ensureOffsetLength( array, offset, length );
final K[] a =
newArray( array, length );
System.arraycopy( array, offset, a, 0, length );
return a;
}
/** Returns a copy of an array.
*
* @param array an array.
* @return a copy of array.
*/
public static K[] copy( final K[] array ) {
return array.clone();
}
/** Fills the given array with the given value.
*
* This method uses a backward loop. It is significantly faster than the corresponding
* method in {@link java.util.Arrays}.
*
* @param array an array.
* @param value the new value for all elements of the array.
*/
public static void fill( final K[] array, final K value ) {
int i = array.length;
while( i-- != 0 ) array[ i ] = value;
}
/** Fills a portion of the given array with the given value.
*
* If possible (i.e., from is 0) this method uses a
* backward loop. In this case, it is significantly faster than the
* corresponding method in {@link java.util.Arrays}.
*
* @param array an array.
* @param from the starting index of the portion to fill (inclusive).
* @param to the end index of the portion to fill (exclusive).
* @param value the new value for all elements of the specified portion of the array.
*/
public static void fill( final K[] array, final int from, int to, final K value ) {
ensureFromTo( array, from, to );
if ( from == 0 ) while( to-- != 0 ) array[ to ] = value;
else for( int i = from; i < to; i++ ) array[ i ] = value;
}
/** Returns true if the two arrays are elementwise equal.
*
* @param a1 an array.
* @param a2 another array.
* @return true if the two arrays are of the same length, and their elements are equal.
* @deprecated Please use the corresponding {@link java.util.Arrays} method, which is intrinsified in recent JVMs.
*/
@Deprecated
public static boolean equals( final K[] a1, final K a2[] ) {
int i = a1.length;
if ( i != a2.length ) return false;
while( i-- != 0 ) if (! ( (a1[ i ]) == null ? (a2[ i ]) == null : (a1[ i ]).equals(a2[ i ]) ) ) return false;
return true;
}
/** Ensures that a range given by its first (inclusive) and last (exclusive) elements fits an array.
*
* This method may be used whenever an array range check is needed.
*
* @param a an array.
* @param from a start index (inclusive).
* @param to an end index (exclusive).
* @throws IllegalArgumentException if from is greater than to.
* @throws ArrayIndexOutOfBoundsException if from or to are greater than the array length or negative.
*/
public static void ensureFromTo( final K[] a, final int from, final int to ) {
Arrays.ensureFromTo( a.length, from, to );
}
/** Ensures that a range given by an offset and a length fits an array.
*
* This method may be used whenever an array range check is needed.
*
* @param a an array.
* @param offset a start index.
* @param length a length (the number of elements in the range).
* @throws IllegalArgumentException if length is negative.
* @throws ArrayIndexOutOfBoundsException if offset is negative or offset+length is greater than the array length.
*/
public static void ensureOffsetLength( final K[] a, final int offset, final int length ) {
Arrays.ensureOffsetLength( a.length, offset, length );
}
private static final int SMALL = 7;
private static final int MEDIUM = 50;
private static void swap( final K x[], final int a, final int b ) {
final K t = x[ a ];
x[ a ] = x[ b ];
x[ b ] = t;
}
private static void vecSwap( final K[] x, int a, int b, final int n ) {
for( int i = 0; i < n; i++, a++, b++ ) swap( x, a, b );
}
private static int med3( final K x[], final int a, final int b, final int c, Comparator comp ) {
int ab = comp.compare( x[ a ], x[ b ] );
int ac = comp.compare( x[ a ], x[ c ] );
int bc = comp.compare( x[ b ], x[ c ] );
return ( ab < 0 ?
( bc < 0 ? b : ac < 0 ? c : a ) :
( bc > 0 ? b : ac > 0 ? c : a ) );
}
private static void selectionSort( final K[] a, final int from, final int to, final Comparator comp ) {
for( int i = from; i < to - 1; i++ ) {
int m = i;
for( int j = i + 1; j < to; j++ ) if ( comp.compare( a[ j ], a[ m ] ) < 0 ) m = j;
if ( m != i ) {
final K u = a[ i ];
a[ i ] = a[ m ];
a[ m ] = u;
}
}
}
private static void insertionSort( final K[] a, final int from, final int to, final Comparator comp ) {
for ( int i = from; ++i < to; ) {
K t = a[ i ];
int j = i;
for ( K u = a[ j - 1 ]; comp.compare( t, u ) < 0; u = a[ --j - 1 ] ) {
a[ j ] = u;
if ( from == j - 1 ) {
--j;
break;
}
}
a[ j ] = t;
}
}
@SuppressWarnings("unchecked")
private static void selectionSort( final K[] a, final int from, final int to ) {
for( int i = from; i < to - 1; i++ ) {
int m = i;
for( int j = i + 1; j < to; j++ ) if ( ( ((Comparable)(a[ j ])).compareTo(a[ m ]) < 0 ) ) m = j;
if ( m != i ) {
final K u = a[ i ];
a[ i ] = a[ m ];
a[ m ] = u;
}
}
}
@SuppressWarnings("unchecked")
private static void insertionSort( final K[] a, final int from, final int to ) {
for ( int i = from; ++i < to; ) {
K t = a[ i ];
int j = i;
for ( K u = a[ j - 1 ]; ( ((Comparable)(t)).compareTo(u) < 0 ); u = a[ --j - 1 ] ) {
a[ j ] = u;
if ( from == j - 1 ) {
--j;
break;
}
}
a[ j ] = t;
}
}
/** Sorts the specified range of elements according to the order induced by the specified
* comparator using quicksort.
*
* The sorting algorithm is a tuned quicksort adapted from Jon L. Bentley and M. Douglas
* McIlroy, “Engineering a Sort Function”, Software: Practice and Experience, 23(11), pages
* 1249−1265, 1993.
*
* @param x the array to be sorted.
* @param from the index of the first element (inclusive) to be sorted.
* @param to the index of the last element (exclusive) to be sorted.
* @param comp the comparator to determine the sorting order.
*
*/
public static void quickSort( final K[] x, final int from, final int to, final Comparator comp ) {
final int len = to - from;
// Selection sort on smallest arrays
if ( len < SMALL ) {
selectionSort( x, from, to, comp );
return;
}
// Choose a partition element, v
int m = from + len / 2; // Small arrays, middle element
if ( len > SMALL ) {
int l = from;
int n = to - 1;
if ( len > MEDIUM ) { // Big arrays, pseudomedian of 9
int s = len / 8;
l = med3( x, l, l + s, l + 2 * s, comp );
m = med3( x, m - s, m, m + s, comp );
n = med3( x, n - 2 * s, n - s, n, comp );
}
m = med3( x, l, m, n, comp ); // Mid-size, med of 3
}
final K v = x[ m ];
// Establish Invariant: v* (v)* v*
int a = from, b = a, c = to - 1, d = c;
while(true) {
int comparison;
while ( b <= c && ( comparison = comp.compare( x[ b ], v ) ) <= 0 ) {
if ( comparison == 0 ) swap( x, a++, b );
b++;
}
while (c >= b && ( comparison = comp.compare( x[ c ], v ) ) >=0 ) {
if ( comparison == 0 ) swap( x, c, d-- );
c--;
}
if ( b > c ) break;
swap( x, b++, c-- );
}
// Swap partition elements back to middle
int s, n = to;
s = Math.min( a - from, b - a );
vecSwap( x, from, b - s, s );
s = Math.min( d - c, n - d - 1 );
vecSwap( x, b, n - s, s );
// Recursively sort non-partition-elements
if ( ( s = b - a ) > 1 ) quickSort( x, from, from + s, comp );
if ( ( s = d - c ) > 1 ) quickSort( x, n - s, n, comp );
}
/** Sorts an array according to the order induced by the specified
* comparator using quicksort.
*
* The sorting algorithm is a tuned quicksort adapted from Jon L. Bentley and M. Douglas
* McIlroy, “Engineering a Sort Function”, Software: Practice and Experience, 23(11), pages
* 1249−1265, 1993.
*
* @param x the array to be sorted.
* @param comp the comparator to determine the sorting order.
*
*/
public static void quickSort( final K[] x, final Comparator comp ) {
quickSort( x, 0, x.length, comp );
}
@SuppressWarnings("unchecked")
private static int med3( final K x[], final int a, final int b, final int c ) {
int ab = ( ((Comparable)(x[ a ])).compareTo(x[ b ]) );
int ac = ( ((Comparable)(x[ a ])).compareTo(x[ c ]) );
int bc = ( ((Comparable)(x[ b ])).compareTo(x[ c ]) );
return ( ab < 0 ?
( bc < 0 ? b : ac < 0 ? c : a ) :
( bc > 0 ? b : ac > 0 ? c : a ) );
}
/** Sorts the specified range of elements according to the natural ascending order using quicksort.
*
* The sorting algorithm is a tuned quicksort adapted from Jon L. Bentley and M. Douglas
* McIlroy, “Engineering a Sort Function”, Software: Practice and Experience, 23(11), pages
* 1249−1265, 1993.
*
* @param x the array to be sorted.
* @param from the index of the first element (inclusive) to be sorted.
* @param to the index of the last element (exclusive) to be sorted.
* @deprecated Use the corresponding {@code sort()} method in {@link java.util.Arrays}.
*/
@SuppressWarnings("unchecked")
@Deprecated
public static void quickSort( final K[] x, final int from, final int to ) {
final int len = to - from;
// Selection sort on smallest arrays
if ( len < SMALL ) {
selectionSort( x, from, to );
return;
}
// Choose a partition element, v
int m = from + len / 2; // Small arrays, middle element
if ( len > SMALL ) {
int l = from;
int n = to - 1;
if ( len > MEDIUM ) { // Big arrays, pseudomedian of 9
int s = len / 8;
l = med3( x, l, l + s, l + 2 * s );
m = med3( x, m - s, m, m + s );
n = med3( x, n - 2 * s, n - s, n );
}
m = med3( x, l, m, n ); // Mid-size, med of 3
}
final K v = x[ m ];
// Establish Invariant: v* (v)* v*
int a = from, b = a, c = to - 1, d = c;
while(true) {
int comparison;
while ( b <= c && ( comparison = ( ((Comparable)(x[ b ])).compareTo(v) ) ) <= 0 ) {
if ( comparison == 0 ) swap( x, a++, b );
b++;
}
while (c >= b && ( comparison = ( ((Comparable)(x[ c ])).compareTo(v) ) ) >=0 ) {
if ( comparison == 0 ) swap( x, c, d-- );
c--;
}
if ( b > c ) break;
swap( x, b++, c-- );
}
// Swap partition elements back to middle
int s, n = to;
s = Math.min( a - from, b - a );
vecSwap( x, from, b - s, s );
s = Math.min( d - c, n - d - 1 );
vecSwap( x, b, n - s, s );
// Recursively sort non-partition-elements
if ( ( s = b - a ) > 1 ) quickSort( x, from, from + s );
if ( ( s = d - c ) > 1 ) quickSort( x, n - s, n );
}
/** Sorts an array according to the natural ascending order using quicksort.
*
* The sorting algorithm is a tuned quicksort adapted from Jon L. Bentley and M. Douglas
* McIlroy, “Engineering a Sort Function”, Software: Practice and Experience, 23(11), pages
* 1249−1265, 1993.
*
* @param x the array to be sorted.
*
* @deprecated Use the corresponding {@code sort()} method in {@link java.util.Arrays}.
*/
@Deprecated
public static void quickSort( final K[] x ) {
quickSort( x, 0, x.length );
}
/** Sorts the specified range of elements according to the natural ascending order using mergesort, using a given support array.
*
* This sort is guaranteed to be stable: equal elements will not be reordered as a result
* of the sort. Moreover, no support arrays will be allocated.
* @param a the array to be sorted.
* @param from the index of the first element (inclusive) to be sorted.
* @param to the index of the last element (exclusive) to be sorted.
* @param supp a support array containing at least to elements.
*/
@SuppressWarnings("unchecked")
public static void mergeSort( final K a[], final int from, final int to, final K supp[] ) {
int len = to - from;
// Insertion sort on smallest arrays
if ( len < SMALL ) {
insertionSort( a, from, to );
return;
}
// Recursively sort halves of a into supp
final int mid = ( from + to ) >>> 1;
mergeSort( supp, from, mid, a );
mergeSort( supp, mid, to, a );
// If list is already sorted, just copy from supp to a. This is an
// optimization that results in faster sorts for nearly ordered lists.
if ( ( ((Comparable)(supp[ mid - 1 ])).compareTo(supp[ mid ]) <= 0 ) ) {
System.arraycopy( supp, from, a, from, len );
return;
}
// Merge sorted halves (now in supp) into a
for( int i = from, p = from, q = mid; i < to; i++ ) {
if ( q >= to || p < mid && ( ((Comparable)(supp[ p ])).compareTo(supp[ q ]) <= 0 ) ) a[ i ] = supp[ p++ ];
else a[ i ] = supp[ q++ ];
}
}
/** Sorts the specified range of elements according to the natural ascending order using mergesort.
*
* This sort is guaranteed to be stable: equal elements will not be reordered as a result
* of the sort. An array as large as a will be allocated by this method.
* @param a the array to be sorted.
* @param from the index of the first element (inclusive) to be sorted.
* @param to the index of the last element (exclusive) to be sorted.
*/
public static void mergeSort( final K a[], final int from, final int to ) {
mergeSort( a, from, to, a.clone() );
}
/** Sorts an array according to the natural ascending order using mergesort.
*
* This sort is guaranteed to be stable: equal elements will not be reordered as a result
* of the sort. An array as large as a will be allocated by this method.
* @param a the array to be sorted.
*/
public static void mergeSort( final K a[] ) {
mergeSort( a, 0, a.length );
}
/** Sorts the specified range of elements according to the order induced by the specified
* comparator using mergesort, using a given support array.
*
* This sort is guaranteed to be stable: equal elements will not be reordered as a result
* of the sort. Moreover, no support arrays will be allocated.
* @param a the array to be sorted.
* @param from the index of the first element (inclusive) to be sorted.
* @param to the index of the last element (exclusive) to be sorted.
* @param comp the comparator to determine the sorting order.
* @param supp a support array containing at least to elements.
*/
@SuppressWarnings("unchecked")
public static void mergeSort( final K a[], final int from, final int to, Comparator comp, final K supp[] ) {
int len = to - from;
// Insertion sort on smallest arrays
if ( len < SMALL ) {
insertionSort( a, from, to, comp );
return;
}
// Recursively sort halves of a into supp
final int mid = ( from + to ) >>> 1;
mergeSort( supp, from, mid, comp, a );
mergeSort( supp, mid, to, comp, a );
// If list is already sorted, just copy from supp to a. This is an
// optimization that results in faster sorts for nearly ordered lists.
if ( comp.compare( supp[ mid - 1 ], supp[ mid ] ) <= 0 ) {
System.arraycopy( supp, from, a, from, len );
return;
}
// Merge sorted halves (now in supp) into a
for( int i = from, p = from, q = mid; i < to; i++ ) {
if ( q >= to || p < mid && comp.compare( supp[ p ], supp[ q ] ) <= 0 ) a[ i ] = supp[ p++ ];
else a[ i ] = supp[ q++ ];
}
}
/** Sorts the specified range of elements according to the order induced by the specified
* comparator using mergesort.
*
* This sort is guaranteed to be stable: equal elements will not be reordered as a result
* of the sort. An array as large as a will be allocated by this method.
*
* @param a the array to be sorted.
* @param from the index of the first element (inclusive) to be sorted.
* @param to the index of the last element (exclusive) to be sorted.
* @param comp the comparator to determine the sorting order.
*/
public static void mergeSort( final K a[], final int from, final int to, Comparator comp ) {
mergeSort( a, from, to, comp, a.clone() );
}
/** Sorts an array according to the order induced by the specified
* comparator using mergesort.
*
* This sort is guaranteed to be stable: equal elements will not be reordered as a result
* of the sort. An array as large as a will be allocated by this method.
* @param a the array to be sorted.
* @param comp the comparator to determine the sorting order.
*/
public static void mergeSort( final K a[], Comparator comp ) {
mergeSort( a, 0, a.length, comp );
}
/**
* Searches a range of the specified array for the specified value using
* the binary search algorithm. The range must be sorted prior to making this call.
* If it is not sorted, the results are undefined. If the range contains multiple elements with
* the specified value, there is no guarantee which one will be found.
*
* @param a the array to be searched.
* @param from the index of the first element (inclusive) to be searched.
* @param to the index of the last element (exclusive) to be searched.
* @param key the value to be searched for.
* @return index of the search key, if it is contained in the array;
* otherwise, (-(insertion point) - 1). The insertion
* point is defined as the the point at which the value would
* be inserted into the array: the index of the first
* element greater than the key, or the length of the array, if all
* elements in the array are less than the specified key. Note
* that this guarantees that the return value will be >= 0 if
* and only if the key is found.
* @see java.util.Arrays
*/
@SuppressWarnings({"unchecked","rawtypes"})
public static int binarySearch( final K[] a, int from, int to, final K key ) {
K midVal;
to--;
while (from <= to) {
final int mid = (from + to) >>> 1;
midVal = a[ mid ];
final int cmp = ((Comparable)midVal).compareTo( key );
if ( cmp < 0 ) from = mid + 1;
else if (cmp > 0) to = mid - 1;
else return mid;
}
return -( from + 1 );
}
/**
* Searches an array for the specified value using
* the binary search algorithm. The range must be sorted prior to making this call.
* If it is not sorted, the results are undefined. If the range contains multiple elements with
* the specified value, there is no guarantee which one will be found.
*
* @param a the array to be searched.
* @param key the value to be searched for.
* @return index of the search key, if it is contained in the array;
* otherwise, (-(insertion point) - 1). The insertion
* point is defined as the the point at which the value would
* be inserted into the array: the index of the first
* element greater than the key, or the length of the array, if all
* elements in the array are less than the specified key. Note
* that this guarantees that the return value will be >= 0 if
* and only if the key is found.
* @see java.util.Arrays
*/
public static int binarySearch( final K[] a, final K key ) {
return binarySearch( a, 0, a.length, key );
}
/**
* Searches a range of the specified array for the specified value using
* the binary search algorithm and a specified comparator. The range must be sorted following the comparator prior to making this call.
* If it is not sorted, the results are undefined. If the range contains multiple elements with
* the specified value, there is no guarantee which one will be found.
*
* @param a the array to be searched.
* @param from the index of the first element (inclusive) to be searched.
* @param to the index of the last element (exclusive) to be searched.
* @param key the value to be searched for.
* @param c a comparator.
* @return index of the search key, if it is contained in the array;
* otherwise, (-(insertion point) - 1). The insertion
* point is defined as the the point at which the value would
* be inserted into the array: the index of the first
* element greater than the key, or the length of the array, if all
* elements in the array are less than the specified key. Note
* that this guarantees that the return value will be >= 0 if
* and only if the key is found.
* @see java.util.Arrays
*/
public static int binarySearch( final K[] a, int from, int to, final K key, final Comparator c ) {
K midVal;
to--;
while (from <= to) {
final int mid = (from + to) >>> 1;
midVal = a[ mid ];
final int cmp = c.compare( midVal, key );
if ( cmp < 0 ) from = mid + 1;
else if (cmp > 0) to = mid - 1;
else return mid; // key found
}
return -( from + 1 );
}
/**
* Searches an array for the specified value using
* the binary search algorithm and a specified comparator. The range must be sorted following the comparator prior to making this call.
* If it is not sorted, the results are undefined. If the range contains multiple elements with
* the specified value, there is no guarantee which one will be found.
*
* @param a the array to be searched.
* @param key the value to be searched for.
* @param c a comparator.
* @return index of the search key, if it is contained in the array;
* otherwise, (-(insertion point) - 1). The insertion
* point is defined as the the point at which the value would
* be inserted into the array: the index of the first
* element greater than the key, or the length of the array, if all
* elements in the array are less than the specified key. Note
* that this guarantees that the return value will be >= 0 if
* and only if the key is found.
* @see java.util.Arrays
*/
public static int binarySearch( final K[] a, final K key, final Comparator c ) {
return binarySearch( a, 0, a.length, key, c );
}
/** Shuffles the specified array fragment using the specified pseudorandom number generator.
*
* @param a the array to be shuffled.
* @param from the index of the first element (inclusive) to be shuffled.
* @param to the index of the last element (exclusive) to be shuffled.
* @param random a pseudorandom number generator (please use a XorShift* generator).
* @return a.
*/
public static K[] shuffle( final K[] a, final int from, final int to, final Random random ) {
for( int i = to - from; i-- != 0; ) {
final int p = random.nextInt( i + 1 );
final K t = a[ from + i ];
a[ from + i ] = a[ from + p ];
a[ from + p ] = t;
}
return a;
}
/** Shuffles the specified array using the specified pseudorandom number generator.
*
* @param a the array to be shuffled.
* @param random a pseudorandom number generator (please use a XorShift* generator).
* @return a.
*/
public static K[] shuffle( final K[] a, final Random random ) {
for( int i = a.length; i-- != 0; ) {
final int p = random.nextInt( i + 1 );
final K t = a[ i ];
a[ i ] = a[ p ];
a[ p ] = t;
}
return a;
}
/** Reverses the order of the elements in the specified array.
*
* @param a the array to be reversed.
* @return a.
*/
public static K[] reverse( final K[] a ) {
final int length = a.length;
for( int i = length / 2; i-- != 0; ) {
final K t = a[ length - i - 1 ];
a[ length - i - 1 ] = a[ i ];
a[ i ] = t;
}
return a;
}
/** A type-specific content-based hash strategy for arrays. */
private static final class ArrayHashStrategy implements Hash.Strategy, java.io.Serializable {
private static final long serialVersionUID = -7046029254386353129L;
public int hashCode( final K[] o ) {
return java.util.Arrays.hashCode( o );
}
public boolean equals( final K[] a, final K[] b ) {
return java.util.Arrays.equals( a, b );
}
}
/** A type-specific content-based hash strategy for arrays.
*
* This hash strategy may be used in custom hash collections whenever keys are
* arrays, and they must be considered equal by content. This strategy
* will handle null correctly, and it is serializable.
*/
@SuppressWarnings({"rawtypes"})
public final static Hash.Strategy HASH_STRATEGY = new ArrayHashStrategy();
}