Java Median median(long[] array)

Description

median

License

Open Source License

Parameter

Parameter	Description
array	a long array.

Return

the median of the values in this array.

Declaration

public static double median(long[] array) 

Method Source Code

//package com.java2s;
// it under the terms of the GNU General Public License as published by      //

public class Main {
    /**/*from   w w  w  .j a  va2s  .co  m*/
     * @param array a long array.
     * @return the median of the values in this array.
     */
    public static double median(long[] array) {
        return median(array, array.length);
    }

    /**
     * @param array a double array.
     * @return the median of the values in this array.
     */
    public static double median(double[] array) {
        return median(array, array.length);
    }

    /**
     * @param array a long array.
     * @param N     the number of values of array which should be considered.
     * @return the median of the first N values in this array.
     */
    public static long median(long array[], int N) {

        long a[] = new long[N + 1];

        System.arraycopy(array, 0, a, 0, N);

        a[N] = Long.MAX_VALUE;

        long v, t;
        int i, j, l = 0;
        int r = N - 1, k1 = r / 2, k2 = r - k1;

        while (r > l) {
            v = a[l];
            i = l;
            j = r + 1;

            for (;;) {
                while (a[++i] < v) {
                }
                while (a[--j] > v) {
                }

                if (i >= j) {
                    break;
                }

                t = a[i];
                a[i] = a[j];
                a[j] = t;
            }

            t = a[j];
            a[j] = a[l];
            a[l] = t;

            if (j <= k1) {
                l = j + 1;
            }

            if (j >= k2) {
                r = j - 1;
            }
        }

        return (a[k1] + a[k2]) / 2;
    }

    /**
     * @param array a double array.
     * @param N     the number of values of array which should be considered.
     * @return the median of the first N values in this array.
     */
    public static double median(double array[], int N) {

        double a[] = new double[N + 1];

        System.arraycopy(array, 0, a, 0, N);

        a[N] = Double.POSITIVE_INFINITY;

        double v, t;
        int i, j, l = 0;
        int r = N - 1, k1 = r / 2, k2 = r - k1;

        while (r > l) {
            v = a[l];
            i = l;
            j = r + 1;

            for (;;) {
                while (a[++i] < v) {
                }
                while (a[--j] > v) {
                }

                if (i >= j) {
                    break;
                }

                t = a[i];
                a[i] = a[j];
                a[j] = t;
            }

            t = a[j];
            a[j] = a[l];
            a[l] = t;

            if (j <= k1) {
                l = j + 1;
            }

            if (j >= k2) {
                r = j - 1;
            }
        }

        return (a[k1] + a[k2]) / 2;
    }
}

Related

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2. median(int x[], int pos1, int pos2, int pos3)
3. median(int[] m)
4. median(int[] vals)
5. median(Integer[] values)
6. median(Number[] array)
7. median(short[] arr)
8. median3(double[] v)
9. median7(double[] v)