1.归并算法排序

exercises/liufq/中等/归并排序/Solution.java

+class Solution {
+    public static void mergeSort(int[] nums) {
+        if (nums == null || nums.length == 0) {
+            return;
+        }
+        int[] helper = new int[nums.length];
+        mergeSort(nums, helper, 0, nums.length - 1);
+    }
+
+    private static void mergeSort(int[] nums, int[] helper, int low, int high) {
+        if (low < high) {
+            int middle = low + (high - low) / 2;
+            mergeSort(nums, helper, low, middle);
+            mergeSort(nums, helper, middle + 1, high);
+            merge(nums, helper, low, middle, high);
+        }
+    }
+
+    private static void merge(int[] nums, int[] helper, int low, int middle, int high) {
+        for (int i = low; i <= high; i++) {
+            helper[i] = nums[i];
+        }
+
+        int left = low;
+        int right = middle + 1;
+        int curr = low;
+        while (left <= middle && right <= high) {
+            if (helper[left] <= helper[right]) {
+                nums[curr++] = helper[left++];
+            } else {
+                nums[curr++] = helper[right++];
+            }
+        }
+
+        int remain = middle - left;
+        for (int i = 0; i <= remain; i++) {
+            nums[curr + i] = helper[left + i];
+        }
+    }
+}
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exercises/liufq/中等/归并排序/exercies.md

+# 归并排序
+
+你需要用归并排序算法,对数组进行排序,并输出按照升序排序的字符数字串
+
+## 输入描述
+
+你需要对输入的数组根据归并排序算法升序排序
+
+## 输出描述
+
+输出按照升序排序的数组
+
+## 输入样例
+
+输入nums数组为:
+1. int[] nums = new int{}[1,2,4,3,5,6,7,8];
+2. int[] nums = new int{}[1,5,6,10,12,15,2,4];
+3. int[] nums = new int{}[1,4,90,12,14,19,3,4];
+
+
+## 输出样例
+1. 1,2,3,4,5,6,7,8
+2. 1,2,4,5,6,10,12,15
+3. 1,3,4,4,12,14,19,90
+
+
+## 提示
+
+无
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exercises/liufq/中等/归并排序/test_cases/1.in

+int[] nums = new int{}[1,2,4,3,5,6,7,8];
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exercises/liufq/中等/归并排序/test_cases/1.out

+1,2,3,4,5,6,7,8
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exercises/liufq/中等/归并排序/test_cases/2.in

+int[] nums = new int{}[1,5,6,10,12,15,2,4];
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exercises/liufq/中等/归并排序/test_cases/2.out

+1,2,4,5,6,10,12,15
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exercises/liufq/中等/归并排序/test_cases/3.in

+int[] nums = new int{}[1,4,90,12,14,19,3,4];
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exercises/liufq/中等/归并排序/test_cases/3.out

+1,3,4,4,12,14,19,90
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