> For the complete documentation index, see [llms.txt](https://mayanktyagi3111.gitbook.io/interview-prep/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://mayanktyagi3111.gitbook.io/interview-prep/strings-arrays-and-2-pointers/rotate-a-matrix-by-90-degree-without-using-any-extra-space.md).

# Rotate a matrix by 90 degree without using any extra space

Given a square matrix, turn it by 90 degrees in anti-clockwise direction without using any extra space.

**Examples:**

```
Input:
 1  2  3
 4  5  6
 7  8  9
Output:
 3  6  9 
 2  5  8 
 1  4  7 
Rotated the input matrix by
90 degrees in anti-clockwise direction.

Input:
 1  2  3  4 
 5  6  7  8 
 9 10 11 12 
13 14 15 16 
Output:
 4  8 12 16 
 3  7 11 15 
 2  6 10 14 
 1  5  9 13
Rotated the input matrix by
90 degrees in anti-clockwise direction.
```

```java
// for 90deg counter clockwise rotation
class Solution {
    static void reverseColumns(int arr[][]) {
        for (int i = 0; i < arr[0].length; i++) {
            for (int j = 0, k = arr[0].length - 1; j < k; j++, k--) {
                int temp = arr[j][i];
                arr[j][i] = arr[k][i];
                arr[k][i] = temp;
            }
        }
    }

    // Function for do transpose of matrix
    static void transpose(int arr[][]) {
        for (int i = 0; i < arr.length; i++) {
            for (int j = i; j < arr[0].length; j++) {
                int temp = arr[j][i];
                arr[j][i] = arr[i][j];
                arr[i][j] = temp;
            }
        }
    }

    static void rotate90(int arr[][]) {
        transpose(arr);
        reverseColumns(arr);
    }
}

// for 90deg clockwise
class Solution {
    public void rotate(int[][] matrix) {
        for (int i = 0; i < matrix.length; i++) {
            for (int j = i; j < matrix.length; j++) {
                int temp = matrix[i][j];
                matrix[i][j] = matrix[j][i];
                matrix[j][i] = temp;
            }
        }
        for (int i = 0; i < matrix.length; i++) {
            for (int j = 0, k = matrix.length - 1; j < k; j++, k--) {
                int temp = matrix[i][j];
                matrix[i][j] = matrix[i][k];
                matrix[i][k] = temp;
            }
        }
    }
}

```