73 lines
2.4 KiB
Java
73 lines
2.4 KiB
Java
/*
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* The MIT License (MIT)
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*
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* Copyright © 2021 xrv <xrv@live.com>
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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package io.github.ehlxr.algorithm.sort;
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import java.util.Arrays;
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/**
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* @author ehlxr
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* @since 2021-12-27 19:06.
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*/
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public class MergeSort {
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public static void main(String[] args) {
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int[] arrs = new int[]{3, 2, 5, 7, 1, 9};
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System.out.println(Arrays.toString(sort(arrs)));
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}
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public static int[] sort(int[] arrs) {
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if (arrs.length <= 1) {
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return arrs;
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}
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int[] a1 = sort(Arrays.copyOfRange(arrs, 0, arrs.length / 2));
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int[] a2 = sort(Arrays.copyOfRange(arrs, arrs.length / 2, arrs.length));
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return merge(a1, a2);
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}
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public static int[] merge(int[] a1, int[] a2) {
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int i = 0;
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int j = 0;
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int[] result = new int[a1.length + a2.length];
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int k = 0;
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while (i < a1.length || j < a2.length) {
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int temp;
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if (i >= a1.length) {
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temp = a2[j++];
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} else if (j >= a2.length) {
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temp = a1[i++];
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} else if (a1[i] <= a2[j]) {// 为了保证算法的稳定性，如果 a1、a2 有相同的元素，保证 a1 的元素在前面
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temp = a1[i++];
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} else {
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temp = a2[j++];
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}
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result[k] = temp;
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k++;
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}
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return result;
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}
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}
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