解析

//! n,n -> for循环耗时n;辅助数组占地n
class Solution {
public:
  void rotate(vector<int> &nums, int k) {
    int n = nums.size();
    vector<int> temp(n);
    for (int i = 0; i < n; ++i) {
        temp[(i+k)%n]=nums[i];
    }
    nums=temp;
  }
};

//! n,1 -> 三次反转耗时2*n;占地常数
class Solution {
public:
  void rotate(vector<int> &nums, int k) {
    int n = nums.size();
    k = k % n;
    if (k == 0)
      return;

    int changePoint = n - k - 1;
    // err1:
    // k不为0时changePoint也可能是0，所以之前判断changePoint为0返回时过不了[1,2]
    // 1这个测试
    reverse(nums, 0, changePoint);
    reverse(nums, changePoint + 1, n - 1);
    reverse(nums, 0, n - 1);
  }
  void reverse(vector<int> &nums, int left, int right) {
    while (left < right) {
      swap(nums[left], nums[right]);
      ++left;
      --right;
    }
  }
};

class Solution {
public:
  void rotate(vector<int> &nums, int k) {
    int n = nums.size();
    k = k % n;
    for (int i = 0; i < k; ++i) {
      int j = i;
      int temp = nums[i];
      do {
        int next = (j + k) % n;
        swap(temp, nums[next]);

      } while (j != i);
      nums[i] = temp;
    }
    return;
  }
};