leecode刷题（3）-- 旋转数组

1) 先将最后一个保存到临时变量
1 2 3 4 5 6 7 8         [8] --- 临时变量
2）位移
_ 1 2 3 4 5 6 7         [8] --- 临时变量
3）将临时变量放到第一个
8 1 2 3 4 5 6 7

public class Rotate {
    public static void rotate(int[] nums, int k) {
        if (nums == null || k == 0 || k == nums.length) {
            return ;
        }
        // 空间复杂度为 O(1)
        int temp = 0;
        while (k > 0) {
            // 每次将最后一位和前一位数值交换
            temp = nums[nums.length - 1];
            for (int i = nums.length -2; i >= 0; i--) {
                nums[i+1] = nums[i];
            }
            //每次将最后一位赋值为第一个
            nums[0] = temp;
            k--;
        }
        for (int num : nums) {
            System.out.print(num + ",");
        }
    }

    public static void main(String[] args) {
        int[] nums = {-1, -100, 3, 99};
        int k = 2;
        rotate(nums, k);
    }
}

class Solution {
    public static void rotate(int[] nums, int k) {
        if (nums == null || k == 0 || k == nums.length) {
            return;
        }
        k = k % nums.length;
        reverse(nums, 0, nums.length - k - 1);
        reverse(nums, nums.length - k, nums.length - 1);
        reverse(nums, 0, nums.length - 1);
    }

    private static void reverse(int[] nums, int start, int end) {
        while (start < end) {
            int temp = nums[start];
            nums[start] = nums[end];
            nums[end] = temp;
            start++;
            end--;
        }
    }
}