INTUITION:

• Left rotation shifts the first k elements to the end of the array.
• Instead of shifting each element, we reverse parts of the array.
• First, reverse the first k elements, then reverse the rest.
• Finally, reverse the whole array to get the rotated version in place.

APPROACH:

• First, reverse the array from the start to the position k (the number of left rotations).
• Next, reverse the rest of the array from position k to the end.
• Finally, reverse the entire array to complete the left rotation.

Time Complexity:O(N)

Space Complexity:O(1)

Here’s the code:

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