Java Array Merge mergeSort(Object[] src, Object[] dest, int low, int high, int off)

Description

Src is the source array that starts at index 0 Dest is the (possibly larger) array destination with a possible offset low is the index in dest to start sorting high is the end index in dest to end sorting off is the offset to generate corresponding low, high in src To be removed in a future release.

License

Apache License

Declaration

private static void mergeSort(Object[] src, Object[] dest, int low, int high, int off) 

Method Source Code

//package com.java2s;
/*/*from w  w  w .  j av  a 2 s.c  o  m*/
 * Copyright 2016 xueyi (1581249005@qq.com)
 *
 * The Smart-Actor Project licenses this file to you 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.
 */

import java.util.*;

public class Main {
    /**
     * Tuning parameter: list size at or below which insertion sort will be
     * used in preference to mergesort.
     * To be removed in a future release.
     */
    private static final int INSERTIONSORT_THRESHOLD = 7;

    /**
     * Src is the source array that starts at index 0
     * Dest is the (possibly larger) array destination with a possible offset
     * low is the index in dest to start sorting
     * high is the end index in dest to end sorting
     * off is the offset to generate corresponding low, high in src
     * To be removed in a future release.
     */
    private static void mergeSort(Object[] src, Object[] dest, int low, int high, int off) {
        int length = high - low;

        // Insertion sort on smallest arrays
        if (length < INSERTIONSORT_THRESHOLD) {
            for (int i = low; i < high; i++)
                for (int j = i; j > low && ((Comparable) dest[j - 1]).compareTo(dest[j]) > 0; j--)
                    swap(dest, j, j - 1);
            return;
        }

        // Recursively sort halves of dest into src
        int destLow = low;
        int destHigh = high;
        low += off;
        high += off;
        int mid = (low + high) >>> 1;
        mergeSort(dest, src, low, mid, -off);
        mergeSort(dest, src, mid, high, -off);

        // If list is already sorted, just copy from src to dest.  This is an
        // optimization that results in faster sorts for nearly ordered lists.
        if (((Comparable) src[mid - 1]).compareTo(src[mid]) <= 0) {
            System.arraycopy(src, low, dest, destLow, length);
            return;
        }

        // Merge sorted halves (now in src) into dest
        for (int i = destLow, p = low, q = mid; i < destHigh; i++) {
            if (q >= high || p < mid && ((Comparable) src[p]).compareTo(src[q]) <= 0)
                dest[i] = src[p++];
            else
                dest[i] = src[q++];
        }
    }

    /**
     * Src is the source array that starts at index 0
     * Dest is the (possibly larger) array destination with a possible offset
     * low is the index in dest to start sorting
     * high is the end index in dest to end sorting
     * off is the offset into src corresponding to low in dest
     * To be removed in a future release.
     */
    private static void mergeSort(Object[] src, Object[] dest, int low, int high, int off, Comparator c) {
        int length = high - low;

        // Insertion sort on smallest arrays
        if (length < INSERTIONSORT_THRESHOLD) {
            for (int i = low; i < high; i++)
                for (int j = i; j > low && c.compare(dest[j - 1], dest[j]) > 0; j--)
                    swap(dest, j, j - 1);
            return;
        }

        // Recursively sort halves of dest into src
        int destLow = low;
        int destHigh = high;
        low += off;
        high += off;
        int mid = (low + high) >>> 1;
        mergeSort(dest, src, low, mid, -off, c);
        mergeSort(dest, src, mid, high, -off, c);

        // If list is already sorted, just copy from src to dest.  This is an
        // optimization that results in faster sorts for nearly ordered lists.
        if (c.compare(src[mid - 1], src[mid]) <= 0) {
            System.arraycopy(src, low, dest, destLow, length);
            return;
        }

        // Merge sorted halves (now in src) into dest
        for (int i = destLow, p = low, q = mid; i < destHigh; i++) {
            if (q >= high || p < mid && c.compare(src[p], src[q]) <= 0)
                dest[i] = src[p++];
            else
                dest[i] = src[q++];
        }
    }

    /**
     * Swaps x[a] with x[b].
     */
    private static void swap(Object[] x, int a, int b) {
        Object t = x[a];
        x[a] = x[b];
        x[b] = t;
    }
}

Related

1. mergeCharArrays(char[] array1, char[] array2)
2. mergeColumnsSafely(int[] arrOriginalColumns, int[] arrExtraColumns)
3. mergeNoDuplicates(String[] in1, String[] in2)
4. mergeParameterVariableNameDescription(String[] parameterType, String[] variableName)
5. mergerBy(String[] target, String seperator)
6. mergeSort(Object[] src, Object[] dest, int low, int high, int off, Comparator c)
7. mergeSortArrays(String[][] arrayArray)
8. mergeSortedInc(long[] a, long[] b)
9. mergeStringArray(String[] array)