Given a square matrix, turn it by 90 degrees in anti-clockwise direction without using any extra space.
Input: 1 2 3 4 5 6 7 8 9 Output: 7 4 1 8 5 2 9 6 3 Input: 1 2 3 4 Output: 3 1 4 2
Approach: The approach is similar to Inplace rotate square matrix by 90 degrees | Set 1. The only thing that is different is to print the elements of cycle in clockwise direction i.e. An N x N matrix will have floor(N/2) square cycles.
For example, a 3 X 3 matrix will have 1 cycle. The cycle is formed by its 1st row, last column, last row, and 1st column.
For each square cycle, we swap the elements involved with the corresponding cell in the matrix in the clockwise direction. We just need a temporary variable for this.
Let size of row and column be 3.
During first iteration –
a[i][j] = Element at first index (leftmost corner top)= 1.
a[j][n-1-i]= Rightmost corner top Element = 3.
a[n-1-i][n-1-j] = Righmost corner bottom element = 9.
a[n-1-j][i] = Leftmost corner bottom element = 7.
Move these elements in the clockwise direction.
During second iteration –
a[i][j] = 2.
a[j][n-1-j] = 6.
a[n-1-i][n-1-j] = 8.
a[n-1-j][i] = 4.
Similarly, move these elements in the clockwise direction.
Below is the implementation of above approach:
13 9 5 1 14 10 6 2 15 11 7 3 16 12 8 4
- Rotate a matrix by 90 degree without using any extra space | Set 2
- Rotate a Matrix by 180 degree
- Print n x n spiral matrix using O(1) extra space
- Rotate the matrix right by K times
- Rotate Matrix Elements
- Rotate each ring of matrix anticlockwise by K elements
- Inplace rotate square matrix by 90 degrees | Set 1
- Element in a matrix starting from which anti-clockwise traversal ends at the last element
- Move matrix elements in given direction and add elements with same value
- Inplace (Fixed space) M x N size matrix transpose | Updated
- Printing Matrix Chain Multiplication (A Space Optimized Solution)
- Check if an array is sorted and rotated clockwise
- Direction at last square block
- Turn an image by 90 degree
- Count possible moves in the given direction in a grid
If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to email@example.com. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.