# Java Program to Rotate all Matrix elements except the diagonal K times by 90 degrees in clockwise direction

Last Updated : 24 Jul, 2022

Given a square matrix mat[][] of dimension N and an integer K, the task is to rotate the matrix by 90 degrees K times without changing the position of the diagonal elements.

Examples:

Input: mat[][] = {{1, 2, 3, 4, 5}, {6, 7, 8, 9, 10}, {11, 12, 13, 14, 15}, {16, 17, 18, 19, 20}, {21, 22, 23, 24, 25}}, K = 1
Output:
1 16 11 6 5
22 7 12 9 2
23 18 13 8 3
24 17 14 19 4
21 20 15 10 25

Input: mat[][] = {{10, 11}, {12, 13}}, K = 2
Output:
10 11
12 13

Approach: The given problem can be solved by using the idea discussed in this article and the fact that the matrix restores after performing clockwise rotation 4 times. Follow the below steps to solve the given problem:

• Update the value of K as K % 4.
• Iterate until K is a positive and perform the following steps:
• Traverse the matrix, for i over the range [0, N / 2) and j over the range[0, N – i – 1) and perform the following steps:
• If the value of i != j and (i + j) != (N – 1), then perform the following steps:
• Store the value of mat[i][j] in a temporary variable temp.
• Update the value of mat[i][j] as mat[N – 1 – j][i].
• Update the value of mat[N – 1 – j][i] as mat[N – 1 -i][N – 1 – j].
• Update the value of mat[N – 1  – i][N – 1 – j] as mat[j][N – 1 – i].
• Update the value of mat[j][N – 1 – i] as temp.
• After completing the above steps, print the updated matrix obtained.

Below is the implementation of the above approach:

## Java

 `// Java program for the above approach` `import` `java.io.*;` `import` `java.lang.*;` `import` `java.util.*;`   `public` `class` `GFG {`   `    ``// Function to print the matrix` `    ``static` `void` `print(``int` `mat[][])` `    ``{` `        ``// Iterate over the rows` `        ``for` `(``int` `i = ``0``; i < mat.length; i++) {`   `            ``// Iterate over the columns` `            ``for` `(``int` `j = ``0``; j < mat[``0``].length; j++)`   `                ``// Print the value` `                ``System.out.print(mat[i][j] + ``" "``);` `          `  `            ``System.out.println();` `        ``}` `    ``}`   `    ``// Function to perform the swapping of` `    ``// matrix elements in clockwise manner` `    ``static` `void` `performSwap(``int` `mat[][], ``int` `i, ``int` `j)` `    ``{` `        ``int` `N = mat.length;`   `        ``// Stores the last row` `        ``int` `ei = N - ``1` `- i;`   `        ``// Stores the last column` `        ``int` `ej = N - ``1` `- j;`   `        ``// Perform the swaps` `        ``int` `temp = mat[i][j];` `        ``mat[i][j] = mat[ej][i];` `        ``mat[ej][i] = mat[ei][ej];` `        ``mat[ei][ej] = mat[j][ei];` `        ``mat[j][ei] = temp;` `    ``}`   `    ``// Function to rotate non - diagonal` `    ``// elements of the matrix K times in` `    ``// clockwise direction` `    ``static` `void` `rotate(``int` `mat[][], ``int` `N, ``int` `K)` `    ``{` `        ``// Update K to K % 4` `        ``K = K % ``4``;`   `        ``// Iterate until K is positive` `        ``while` `(K-- > ``0``) {`   `            ``// Iterate each up to N/2-th row` `            ``for` `(``int` `i = ``0``; i < N / ``2``; i++) {`   `                ``// Iterate each column` `                ``// from i to N - i - 1` `                ``for` `(``int` `j = i; j < N - i - ``1``; j++) {`   `                    ``// Check if the element` `                    ``// at i, j is not a` `                    ``// diagonal element` `                    ``if` `(i != j && (i + j) != N - ``1``) {`   `                        ``// Perform the swapping` `                        ``performSwap(mat, i, j);` `                    ``}` `                ``}` `            ``}` `        ``}`   `        ``// Print the matrix` `        ``print(mat);` `    ``}` `  `  `    ``// Driver Code` `    ``public` `static` `void` `main(String[] args)` `    ``{`   `        ``int` `K = ``5``;` `        ``int` `mat[][] = {` `            ``{ ``1``, ``2``, ``3``, ``4` `},` `            ``{ ``6``, ``7``, ``8``, ``9` `},` `            ``{ ``11``, ``12``, ``13``, ``14` `},` `            ``{ ``16``, ``17``, ``18``, ``19` `},` `        ``};` `      `  `        ``int` `N = mat.length;` `        ``rotate(mat, N, K);` `    ``}` `}`   `// This code is contributed by Kingash.`

Output:

```  1 11  6  4
17  7  8  2
18 12 13  3
16 14  9 19```

Time Complexity: O(N3) since using three inner loop one while and two for loop
Auxiliary Space: O(1)

Please refer complete article on Rotate all Matrix elements except the diagonal K times by 90 degrees in clockwise direction for more details!

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