smile.sort

Class QuickSelect

java.lang.Object

smile.sort.QuickSelect

public class QuickSelect
extends Object

Selection is asking for the k th smallest element out of n elements. This class implements the fastest general method for selection based on partitioning, exactly as done in the Quicksort algorithm.

The most common use of selection is in the statistical characterization of a set of data. One often wants to know the median element (quantile p = 1/2) in an array or the top and bottom quartile elements (quantile p = 1/4, 3/4).

Author:

Haifeng Li

Constructor Summary

Constructors

Constructor and Description
QuickSelect()

Method Summary

Modifier and Type	Method and Description
static double	median(double[] a) Find the median of an array of type double.
static float	median(float[] a) Find the median of an array of type float.
static int	median(int[] a) Find the median of an array of type integer.
static <T extends Comparable<? super T>> T	median(T[] a) Find the median of an array of type double.
static double	q1(double[] a) Find the first quantile (p = 1/4) of an array of type double.
static float	q1(float[] a) Find the first quantile (p = 1/4) of an array of type float.
static int	q1(int[] a) Find the first quantile (p = 1/4) of an array of type integer.
static <T extends Comparable<? super T>> T	q1(T[] a) Find the first quantile (p = 1/4) of an array of type double.
static double	q3(double[] a) Find the third quantile (p = 3/4) of an array of type double.
static float	q3(float[] a) Find the third quantile (p = 3/4) of an array of type float.
static int	q3(int[] a) Find the third quantile (p = 3/4) of an array of type integer.
static <T extends Comparable<? super T>> T	q3(T[] a) Find the third quantile (p = 3/4) of an array of type double.
static double	select(double[] arr, int k) Given k in [0, n-1], returns an array value from arr such that k array values are less than or equal to the one returned.
static float	select(float[] arr, int k) Given k in [0, n-1], returns an array value from arr such that k array values are less than or equal to the one returned.
static int	select(int[] arr, int k) Given k in [0, n-1], returns an array value from arr such that k array values are less than or equal to the one returned.
static <T extends Comparable<? super T>> T	select(T[] arr, int k) Given k in [0, n-1], returns an array value from arr such that k array values are less than or equal to the one returned.

Methods inherited from class java.lang.Object

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

Constructor Detail

QuickSelect

public QuickSelect()

Method Detail

select

public static int select(int[] arr,
                         int k)

Given k in [0, n-1], returns an array value from arr such that k array values are less than or equal to the one returned. The input array will be rearranged to have this value in location arr[k], with all smaller elements moved to arr[0, k-1] (in arbitrary order) and all larger elements in arr[k+1, n-1] (also in arbitrary order).

select

public static float select(float[] arr,
                           int k)

Given k in [0, n-1], returns an array value from arr such that k array values are less than or equal to the one returned. The input array will be rearranged to have this value in location arr[k], with all smaller elements moved to arr[0, k-1] (in arbitrary order) and all larger elements in arr[k+1, n-1] (also in arbitrary order).

select

public static double select(double[] arr,
                            int k)

Given k in [0, n-1], returns an array value from arr such that k array values are less than or equal to the one returned. The input array will be rearranged to have this value in location arr[k], with all smaller elements moved to arr[0, k-1] (in arbitrary order) and all larger elements in arr[k+1, n-1] (also in arbitrary order).

select

public static <T extends Comparable<? super T>> T select(T[] arr,
                                                         int k)

Given k in [0, n-1], returns an array value from arr such that k array values are less than or equal to the one returned. The input array will be rearranged to have this value in location arr[k], with all smaller elements moved to arr[0, k-1] (in arbitrary order) and all larger elements in arr[k+1, n-1] (also in arbitrary order).

median

public static int median(int[] a)

Find the median of an array of type integer.

median

public static float median(float[] a)

Find the median of an array of type float.

median

public static double median(double[] a)

Find the median of an array of type double.

median

public static <T extends Comparable<? super T>> T median(T[] a)

Find the median of an array of type double.

q1

public static int q1(int[] a)

Find the first quantile (p = 1/4) of an array of type integer.

q1

public static float q1(float[] a)

Find the first quantile (p = 1/4) of an array of type float.

q1

public static double q1(double[] a)

Find the first quantile (p = 1/4) of an array of type double.

q1

public static <T extends Comparable<? super T>> T q1(T[] a)

Find the first quantile (p = 1/4) of an array of type double.

q3

public static int q3(int[] a)

Find the third quantile (p = 3/4) of an array of type integer.

q3

public static float q3(float[] a)

Find the third quantile (p = 3/4) of an array of type float.

q3

public static double q3(double[] a)

Find the third quantile (p = 3/4) of an array of type double.

q3

public static <T extends Comparable<? super T>> T q3(T[] a)

Find the third quantile (p = 3/4) of an array of type double.