089_Rotate_Array

Given an integer array nums, rotate the array to the right by k steps, where k is non-negative.

Input: nums = [1,2,3,4,5,6,7], k = 3
Output: [5,6,7,1,2,3,4]

BruteForce (TLE)

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

        for(int i = 0; i < k; i++) {
            nums.insert(nums.begin(), nums.back());
            nums.pop_back();
        }
    }
};

optimized with extra space

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

        for(int i = n - k; i < n; i++) {
            ans.push_back(nums[i]);
        }
        for(int i = 0; i < n - k; i++) {
            ans.push_back(nums[i]);
        }

        nums = ans;
    }
};

Reversal Approach

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