diff --git a/budd-common/src/main/java/io/github/ehlxr/algorithm/sort/MergeSort.java b/budd-common/src/main/java/io/github/ehlxr/algorithm/sort/MergeSort.java new file mode 100644 index 0000000..5b144e9 --- /dev/null +++ b/budd-common/src/main/java/io/github/ehlxr/algorithm/sort/MergeSort.java @@ -0,0 +1,72 @@ +/* + * The MIT License (MIT) + * + * Copyright © 2021 xrv + * + * Permission is hereby granted, free of charge, to any person obtaining a copy + * of this software and associated documentation files (the "Software"), to deal + * in the Software without restriction, including without limitation the rights + * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell + * copies of the Software, and to permit persons to whom the Software is + * furnished to do so, subject to the following conditions: + * + * The above copyright notice and this permission notice shall be included in + * all copies or substantial portions of the Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE + * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN + * THE SOFTWARE. + */ + +package io.github.ehlxr.algorithm.sort; + +import java.util.Arrays; + +/** + * @author ehlxr + * @since 2021-12-27 19:06. + */ +public class MergeSort { + public static void main(String[] args) { + int[] arrs = new int[]{3, 2, 5, 7, 1, 9}; + System.out.println(Arrays.toString(sort(arrs))); + } + + public static int[] sort(int[] arrs) { + if (arrs.length <= 1) { + return arrs; + } + int[] a1 = sort(Arrays.copyOfRange(arrs, 0, arrs.length / 2)); + int[] a2 = sort(Arrays.copyOfRange(arrs, arrs.length / 2, arrs.length)); + + return merge(a1, a2); + } + + public static int[] merge(int[] a1, int[] a2) { + int i = 0; + int j = 0; + int[] result = new int[a1.length + a2.length]; + int k = 0; + while (i < a1.length || j < a2.length) { + int temp; + if (i >= a1.length) { + temp = a2[j++]; + } else if (j >= a2.length) { + temp = a1[i++]; + } 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 + temp = a1[i++]; + } else { + temp = a2[j++]; + } + + result[k] = temp; + k++; + } + + return result; + } +}