二刷189

Author: diguage

docs/0189-rotate-array.adoc

@@ -1,48 +1,82 @@
 [#0189-rotate-array]
-= 189. Rotate Array
+= 189. 轮转数组
 
-{leetcode}/problems/rotate-array/[LeetCode - Rotate Array^]
+https://leetcode.cn/problems/rotate-array/[LeetCode - 189. 轮转数组 ^]
 
-发现官网测试用例少了一个特殊情况：如果 `k` 大于两倍数组长度，提交的测试就会报错，但是官网却显示通过。
+给定一个整数数组 `nums`，将数组中的元素向右轮转 `k` 个位置，其中 `k` 是非负数。
 
-数组反转的方法也不错！反转时，直接使用界限的值进行加减比较简单省事！
+*示例 1:*
 
-Given an array, rotate the array to the right by _k_ steps, where _k_ is non-negative.
+....
+输入: nums = [1,2,3,4,5,6,7], k = 3
+输出: [5,6,7,1,2,3,4]
+解释:
+向右轮转 1 步: [7,1,2,3,4,5,6]
+向右轮转 2 步: [6,7,1,2,3,4,5]
+向右轮转 3 步: [5,6,7,1,2,3,4]
+....
 
-*Example 1:*
+*示例 2:*
 
-[subs="verbatim,quotes,macros"]
-----
-*Input:* `[1,2,3,4,5,6,7]` and _k_ = 3
-*Output:* `[5,6,7,1,2,3,4]`
-*Explanation:*
-rotate 1 steps to the right: `[7,1,2,3,4,5,6]`
-rotate 2 steps to the right: `[6,7,1,2,3,4,5]
-`rotate 3 steps to the right: `[5,6,7,1,2,3,4]`
-----
+....
+输入：nums = [-1,-100,3,99], k = 2
+输出：[3,99,-1,-100]
+解释:
+向右轮转 1 步: [99,-1,-100,3]
+向右轮转 2 步: [3,99,-1,-100]
+....
 
-*Example 2:*
+*提示：*
+
+* `1 \<= nums.length \<= 10^5^`
+* `-2^31^ \<= nums[i] \<= 2^31^ - 1`
+* `0 \<= k \<= 10^5^`
+
+
+*进阶：*
+
+* 尽可能想出更多的解决方案，至少有 *三种* 不同的方法可以解决这个问题。
+* 你可以使用空间复杂度为 stem:[O(1)] 的 **原地 **算法解决这个问题吗？
 
-[subs="verbatim,quotes,macros"]
-----
-*Input:* `[-1,-100,3,99]` and _k_ = 2
-*Output:* [3,99,-1,-100]
-*Explanation:* 
-rotate 1 steps to the right: [99,-1,-100,3]
-rotate 2 steps to the right: [3,99,-1,-100]
-----
 
-*Note:*
+== 思路分析
 
+注意：这里是轮转数组！如果 `k > nums.length`，那么轮转 `k % nums.length` 次和轮转 `k` 次的效果是一样的。
 
-* Try to come up as many solutions as you can, there are at least 3 different ways to solve this problem.
-* Could you do it in-place with O(1) extra space?
+整个过程如下：
 
+AB → rev(B)rev(A) → rev(rev(B))rev(rev(A)) → BA
 
+image::images/0189-10.png[{image_attr}]
 
 [[src-0189]]
+[tabs]
+====
+一刷::
++
+--
 [{java_src_attr}]
 ----
 include::{sourcedir}/_0189_RotateArray.java[tag=answer]
 ----
+--
+
+二刷::
++
+--
+[{java_src_attr}]
+----
+include::{sourcedir}/_0189_RotateArray_2.java[tag=answer]
+----
+--
+====
+
+
+发现官网测试用例少了一个特殊情况：如果 `k` 大于两倍数组长度，提交的测试就会报错，但是官网却显示通过。
+
+数组反转的方法也不错！反转时，直接使用界限的值进行加减比较简单省事！
+
+== 参考资料
 
+. https://leetcode.cn/problems/rotate-array/solutions/2784427/tu-jie-yuan-di-zuo-fa-yi-tu-miao-dong-py-ryfv/[189. 轮转数组 - 原地做法，一图秒懂！附数学证明^]
+. https://leetcode.cn/problems/rotate-array/solutions/551039/xuan-zhuan-shu-zu-by-leetcode-solution-nipk/[189. 轮转数组 - 官方题解^] -- 环状替换有意思！

docs/images/0189-10.png

@@ -388,6 +388,11 @@ endif::[]
 |{doc_base_url}/0031-next-permutation.adoc[题解]
 |❌ 明白大概意思，思路不够条理，写不出代码。
 
+|{counter:codes}
+|{leetcode_base_url}/rotate-array/[189. Rotate Array^]
+|{doc_base_url}/0189-rotate-array.adoc[题解]
+|❌ 题目理解错误，是轮转数组，不是旋转数组。
+
 |===
 
 截止目前，本轮练习一共完成 {codes2503} 道题。

logbook/202503.adoc

@@ -46,6 +46,9 @@ public class _0189_RotateArray {
      * Memory Usage: 37.4 MB, less than 100.00% of Java online submissions for Rotate Array.
      *
      * Copy from: https://leetcode.com/problems/rotate-array/solution/[Rotate Array solution - LeetCode]
+     *
+     * @author D瓜哥 · https://www.diguage.com
+     * @since 2020-01-05 13:05
      */
     public void rotate(int[] nums, int k) {
         if (Objects.isNull(nums) || nums.length == 0 || k % nums.length == 0) {

src/main/java/com/diguage/algo/leetcode/_0189_RotateArray.java

@@ -0,0 +1,33 @@
+package com.diguage.algo.leetcode;
+
+public class _0189_RotateArray_2 {
+  // tag::answer[]
+
+  /**
+   * AB → rev(B)rev(A) → rev(rev(B))rev(rev(A)) → BA
+   *
+   * @author D瓜哥 · https://www.diguage.com
+   * @since 2020-01-05 13:05
+   */
+  public void rotate(int[] nums, int k) {
+    int len = nums.length;
+    k %= len;
+    if (k == 0) {
+      return;
+    }
+    reverse(nums, 0, len - 1);
+    reverse(nums, 0, k - 1);
+    reverse(nums, k, len - 1);
+  }
+
+  private void reverse(int[] nums, int start, int end) {
+    while (start < end) {
+      int temp = nums[start];
+      nums[start] = nums[end];
+      nums[end] = temp;
+      start++;
+      end--;
+    }
+  }
+  // end::answer[]
+}