To rotate a matrix 90 degrees anti-clockwise in-place, we need to rearrange its elements without using an extra matrix. Instead of manually tracking every element, we can achieve this by performing two simple and reversible operations:

Transpose the matrix : Flip it over its diagonal.
Reverse each column :To simulate the anti-clockwise effect.

Why does this work?

Transposing changes rows into columns.
Reversing each column flips the newly formed rows (i.e., original columns), giving us the anti-clockwise rotation.

Normalize the matrix size (assume it's N x N for square matrix).
Transpose the matrix:
- Swap elements at positions (i, j) and (j, i) for all i < j.
Reverse each column:
- For each column, swap the top and bottom elements moving towards the center.
Matrix will now be rotated anti-clockwise by 90 degrees in-place.

Code

#include <bits/stdc++.h>
using namespace std;

class Solution {
public:
    // Function to rotate the matrix 90 degrees anti-clockwise in-place
    void rotateAntiClockwise(vector<vector<int>>& matrix) {
        int n = matrix.size();

        // Step 1: Transpose the matrix
        for (int i = 0; i < n; ++i) {
            for (int j = i + 1; j < n; ++j) {
                // Swap elements across the diagonal
                swap(matrix[i][j], matrix[j][i]);
            }
        }

        // Step 2: Reverse each column to get anti-clockwise rotation
        for (int j = 0; j < n; ++j) {
            int top = 0, bottom = n - 1;
            while (top < bottom) {
                // Swap elements in the column from top to bottom
 