# Java Program to Modify a matrix by rotating ith row exactly i times in clockwise direction

• Last Updated : 30 May, 2022

Given a matrix mat[][] of dimensions M * N, the task is to print the matrix obtained after rotating every ith row of the matrix i times in a clockwise direction.

Examples:

Input: mat[][] = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}}
Output:
1 2 3
6 4 5
8 9 7
Explanation:
The 0th row is rotated 0 times. Therefore, the 0th row remains the same as {1, 2, 3}.
The 1st row is rotated 1 times. Therefore, the 1st row modifies to {6, 4, 5}.
The 2nd row is rotated 2 times. Therefore, the 2nd row modifies to {8, 9, 7}.
After completing the above operations, the given matrix modifies to {{1, 2, 3}, {6, 4, 5}, {8, 9, 7}}.

Input: mat[][] = {{1, 2, 3, 4}, {4, 5, 6, 7}, {7, 8, 9, 8}, {7, 8, 9, 8}}
Output:
1 2 3 4
7 4 5 6
9 8 7 8
8 9 8 7

Approach: Follow the steps below to solve the problem:

Below is the implementation of the above approach:

## Java

 `// java program for the above approach` `import` `java.io.*;` `import` `java.lang.*;` `import` `java.util.*;`   `class` `GFG {`   `  ``// Function to reverse arr[] from start to end` `  ``static` `void` `reverse(``int` `arr[], ``int` `start, ``int` `end)` `  ``{` `    ``while` `(start < end) {` `      ``int` `temp = arr[start];` `      ``arr[start] = arr[end];` `      ``arr[end] = temp;` `      ``start++;` `      ``end--;` `    ``}` `  ``}`   `  ``// Function to rotate every i-th` `  ``// row of the matrix i times` `  ``static` `void` `rotateMatrix(``int` `mat[][])` `  ``{` `    ``int` `i = ``0``;`   `    ``// Traverse the matrix row-wise` `    ``for` `(``int` `rows[] : mat) {`   `      ``// Reverse the current row` `      ``reverse(rows, ``0``, rows.length - ``1``);`   `      ``// Reverse the first i elements` `      ``reverse(rows, ``0``, i - ``1``);`   `      ``// Reverse the last (N - i) elements` `      ``reverse(rows, i, rows.length - ``1``);`   `      ``// Increment count` `      ``i++;` `    ``}`   `    ``// Print final matrix` `    ``for` `(``int` `rows[] : mat) {` `      ``for` `(``int` `cols : rows) {` `        ``System.out.print(cols + ``" "``);` `      ``}` `      ``System.out.println();` `    ``}` `  ``}`   `  ``// Driver Code` `  ``public` `static` `void` `main(String[] args)` `  ``{`   `    ``int` `mat[][] = { { ``1``, ``2``, ``3` `}, ` `                   ``{ ``4``, ``5``, ``6` `}, ` `                   ``{ ``7``, ``8``, ``9` `} };`   `    ``rotateMatrix(mat);` `  ``}` `}`   `// This code is contributed by Kingash.`

Output:

```1 2 3
6 4 5
8 9 7```

Time Complexity: O(N*M), as we are using nested loops to traverse N*M times.

Auxiliary Space: O(1), as we are not using any extra space.

Please refer complete article on Modify a matrix by rotating ith row exactly i times in clockwise direction for more details!

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