it.unimi.dsi.fastutil

Class Arrays

java.lang.Object

it.unimi.dsi.fastutil.Arrays

public class Arrays
extends Object

A class providing static methods and objects that do useful things with arrays.

In addition to commodity methods, this class contains Swapper-based implementations of quicksort and of a stable, in-place mergesort. These generic sorting methods can be used to sort any kind of list, but they find their natural usage, for instance, in sorting arrays in parallel.

See Also:

Arrays

Method Summary

Methods

Modifier and Type	Method and Description
static void	ensureFromTo(int arrayLength, int from, int to) Ensures that a range given by its first (inclusive) and last (exclusive) elements fits an array of given length.
static void	ensureOffsetLength(int arrayLength, int offset, int length) Ensures that a range given by an offset and a length fits an array of given length.
static void	mergeSort(int from, int to, IntComparator c, Swapper swapper) Sorts the specified range of elements using the specified swapper and according to the order induced by the specified comparator using mergesort.
static void	quickSort(int from, int to, IntComparator comp, Swapper swapper) Sorts the specified range of elements using the specified swapper and according to the order induced by the specified comparator using quicksort.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

ensureFromTo

public static void ensureFromTo(int arrayLength,
                int from,
                int to)

Ensures that a range given by its first (inclusive) and last (exclusive) elements fits an array of given length.

This method may be used whenever an array range check is needed.

Parameters:

arrayLength - an array length.

from - a start index (inclusive).

to - an end index (inclusive).

Throws:

IllegalArgumentException - if from is greater than to.

ArrayIndexOutOfBoundsException - if from or to are greater than arrayLength or negative.

ensureOffsetLength

public static void ensureOffsetLength(int arrayLength,
                      int offset,
                      int length)

Ensures that a range given by an offset and a length fits an array of given length.

This method may be used whenever an array range check is needed.

Parameters:

arrayLength - an array length.

offset - a start index for the fragment

length - a length (the number of elements in the fragment).

Throws:

IllegalArgumentException - if length is negative.

ArrayIndexOutOfBoundsException - if offset is negative or offset+length is greater than arrayLength.

mergeSort

public static void mergeSort(int from,
             int to,
             IntComparator c,
             Swapper swapper)

Sorts the specified range of elements using the specified swapper and 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. The sorting algorithm is an in-place mergesort that is significantly slower than a standard mergesort, as its running time is O(n (log n)²), but it does not allocate additional memory; as a result, it can be used as a generic sorting algorithm.

Parameters:

from - the index of the first element (inclusive) to be sorted.

to - the index of the last element (exclusive) to be sorted.

c - the comparator to determine the order of the generic data (arguments are positions).

swapper - an object that knows how to swap the elements at any two positions.

quickSort

public static void quickSort(int from,
             int to,
             IntComparator comp,
             Swapper swapper)

Sorts the specified range of elements using the specified swapper and 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.

Parameters:

from - the index of the first element (inclusive) to be sorted.

to - the index of the last element (exclusive) to be sorted.

comp - the comparator to determine the order of the generic data.

swapper - an object that knows how to swap the elements at any two positions.