189. Rotate Array

Use Build-in Reverse() Function

class Solution {
public:
    void rotate(vector<int>& nums, int k)
    {
        reverse(nums.begin(), nums.end());
        k %= nums.size();

        reverse(nums.begin(), nums.begin() + k);
        reverse(nums.begin() + k, nums.end());
    }
};

• T: $O(N)$
• S: $O(1)$

Two Pointers

class Solution {
public:
    void rotate(vector<int>& nums, int k)
    {
        int left = 0, right = nums.size() - 1;
        reverseArray(nums, left, right);
        k %= nums.size();

        left = 0, right = k - 1;
        reverseArray(nums, left, right);

        left = k, right = nums.size() - 1;
        reverseArray(nums, left, right);
    }
    void reverseArray(vector<int>& nums, int left, int right)
    {
        while (left < right)
        {
            swap(nums[left], nums[right]);
            ++left; --right;
        }
    }
};

• T: $O(N)$
• S: $O(1)$