leetcode-189-旋转数组

问题：

package com.example.demo;

import sun.security.util.Length;

public class Test189 {

    /**
     * 方法一：暴力解法
     */
    public void rotate(int[] nums, int k) {

        for (int i = 0; i < k; i++) {
            int pre = nums[nums.length - 1];
            for (int j = 0; j < nums.length; j++) {
                int temp = nums[j];
                nums[j] = pre;
                pre = temp;
            }
        }
    }

    /**
     * 方法二：使用额外数组法
     */
    public void rotate1(int[] nums, int k) {
        int len = nums.length;
        int[] res = new int[len];
        for (int i = 0; i < len; i++) {
            res[(i + k) % len] = nums[i];
        }
        for (int i = 0; i < len; i++) {
            nums[i] = res[i];
        }
    }

    /**
     * 方法三：三步翻转法 ********
     */
    public void rotate2(int[] nums, int k) {
        int len = nums.length;
        //对k重新复制，放置数组越界，当len = 4时，k = 5和 k = 1的效果相同
        k = k % len;
        reverseNums(nums, 0, len - 1);
        reverseNums(nums, 0, k - 1);
        reverseNums(nums, k, len - 1);
    }

    /**
     * 交换指定位置的值
     */
    private void reverseNums(int[] nums, int left, int right) {
        while (left <= right) {
            int temp = nums[left];
            nums[left] = nums[right];
            nums[right] = temp;
            left++;
            right--;
        }
    }

    private void swapArr(int[] nums, int pointer, int cur) {
        int temp = nums[pointer];
        nums[pointer] = nums[cur];
        nums[cur] = temp;
    }

    public static void main(String[] args) {
        Test189 t = new Test189();
        int[] arr = {1, 2, 3, 4, 5, 6};
        t.rotate2(arr, 8);
        for (int i : arr) {
            System.out.print(i + " ");
        }
    }
}