MergeSort 归并排序

Author: BGMer7

src/com/gatsby/utils/SortUtil.java

@@ -1,5 +1,7 @@
 package com.gatsby.utils;
 
+import java.util.Arrays;
+
 /**
  * @ClassName: SortUtil
  * @Description: 排序类
@@ -8,13 +10,15 @@
  */
 
 public class SortUtil {
+    static int[] tmp;
+
     /**
-     * @MethodName:  quickSort
+     * @MethodName: quickSort
      * @Parameter: [nums, begin, end]
      * @Return void
      * @Description: 快速排序
      * @author: Gatsby
-     * @date:  2022/7/25 15:20
+     * @date: 2022/7/25 15:20
      */
     public static void quickSort(int[] nums, int begin, int end) {
         if (begin < end) {
@@ -43,6 +47,48 @@ public static void quickSort(int[] nums, int begin, int end) {
             quickSort(nums, j + 1, end);
         }
     }
+
+
+    public static int[] mergeSort(int[] nums) {
+        tmp = new int[nums.length];
+        merge(nums, 0, nums.length - 1);
+        return nums;
+    }
+
+    private static void merge(int[] nums, int left, int right) {
+        if (left >= right) return;
+
+        int mid = (right + left) >> 1;
+        merge(nums, left, mid);
+        merge(nums, mid + 1, right);
+
+        int i = left;
+        // 如果数组只有一个那就不会操作了
+        int j = mid + 1;
+        int count = 0;
+        while (i <= mid && j <= right) {
+            if (nums[i] <= nums[j]) {
+                tmp[count++] = nums[i++];
+            } else {
+                tmp[count++] = nums[j++];
+            }
+        }
+        // System.out.println(Arrays.toString(tmp));
+        if (i <= mid) {
+            System.arraycopy(nums, i, tmp, count, mid - i + 1);
+        }
+
+        if (j <= right) {
+            System.arraycopy(nums, j, tmp, count, right - j + 1);
+        }
+        System.arraycopy(tmp, 0, nums, left, right - left + 1);
+    }
+
+    public static void main(String[] args) {
+        int[] nums = {6, 2, 5, 3, 8, 3, 1, 6, 3, 4};
+        nums = mergeSort(nums);
+        System.out.println(Arrays.toString(nums));
+    }
 }