48. Rotate Image.cpp

/*
You are given an n x n 2D matrix representing an image, rotate the image by 90 degrees (clockwise).
You have to rotate the image in-place, which means you have to modify the input 2D matrix directly. DO NOT allocate another 2D matrix and do the rotation.
 
Example 1:
Input: matrix = [[1,2,3],[4,5,6],[7,8,9]]
Output: [[7,4,1],[8,5,2],[9,6,3]]
Example 2:
Input: matrix = [[5,1,9,11],[2,4,8,10],[13,3,6,7],[15,14,12,16]]
Output: [[15,13,2,5],[14,3,4,1],[12,6,8,9],[16,7,10,11]]
 
Constraints:
n == matrix.length == matrix[i].length
1 <= n <= 20
-1000 <= matrix[i][j] <= 1000
*/
class Solution {
public:
    void rotate(vector<vector<int>>& matrix) {
        vector<int>v;
        int s=matrix.size();
        for(int i=matrix.size()-1;i>=0;i--){
            for(int j=0;j<matrix[i].size();j++){
                v.push_back(matrix[i][j]);
            }
        }
        int k=0;
        for(int j=0;j<matrix.size();j++){
            for(int i=0;i<matrix[j].size();i++){
                matrix[i][j]=v[k];
                k++;
            }
        }
    }
};


// updated solution 

class Solution {
public:
    void rotate(vector<vector<int>>& matrix) {
        int n=matrix.size();
        for(int i=0;i<n;i++){

              for(int j=0;j<i;j++){
             swap(matrix[i][j],matrix[j][i]);
              }
        }
        for(int i=0;i<n;i++){
        reverse(matrix[i].begin(),matrix[i].end());
        }
    }
};