update at 2021-12-28 10:08:53 by ehlxr

budd-common/src/main/java/io/github/ehlxr/algorithm/sort/MergeSort.java

@@ -0,0 +1,72 @@
+/*
+ * The MIT License (MIT)
+ *
+ * Copyright © 2021 xrv <xrg@live.com>
+ *
+ * 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;
+    }
+}