Rotate Matrix Elements - GeeksforGeeks

Rotate Matrix Elements - GeeksforGeeks
Given a matrix, clockwise rotate elements in it.

Input
1 2 3
4 5 6
7 8 9

Output:
4 1 2
7 5 3
8 9 6

For 4*4 matrix
Input:
1 2 3 4 
5 6 7 8
9 10 11 12
13 14 15 16

Output:
5 1 2 3
9 10 6 4
13 11 7 8
14 15 16 12

The idea is to use loops similar to the program for printing a matrix in spiral form. One by one rotate all rings of elements, starting from the outermost. To rotate a ring, we need to do following.
    1) Move elements of top row.
    2) Move elements of last column.
    3) Move elements of bottom row.
    4) Move elements of first column.
Repeat above steps for inner ring while there is an inner ring.

// A function to rotate a matrix mat[][] of size R x C.

// Initially, m = R and n = C

void rotatematrix(int m, int n, int mat[R][C])

{

    int row = 0, col = 0;

    int prev, curr;

 

    /*

       row - Staring row index

       m - ending row index

       col - starting column index

       n - ending column index

       i - iterator

    */

    while (row < m && col < n)

    {

 

        if (row + 1 == m || col + 1 == n)

            break;

 

        // Store the first element of next row, this

        // element will replace first element of current

        // row

        prev = mat[row + 1][col];

 

         /* Move elements of first row from the remaining rows */

        for (int i = col; i < n; i++)

        {

            curr = mat[row][i];

            mat[row][i] = prev;

            prev = curr;

        }

        row++;

 

        /* Move elements of last column from the remaining columns */

        for (int i = row; i < m; i++)

        {

            curr = mat[i][n-1];

            mat[i][n-1] = prev;

            prev = curr;

        }

        n--;

 

         /* Move elements of last row from the remaining rows */

        if (row < m)

        {

            for (int i = n-1; i >= col; i--)

            {

                curr = mat[m-1][i];

                mat[m-1][i] = prev;

                prev = curr;

            }

        }

        m--;

 

        /* Move elements of first column from the remaining rows */

        if (col < n)

        {

            for (int i = m-1; i >= row; i--)

            {

                curr = mat[i][col];

                mat[i][col] = prev;

                prev = curr;

            }

        }

        col++;

    }

 

    // Print rotated matrix

    for (int i=0; i<R; i++)

    {

        for (int j=0; j<C; j++)

          cout << mat[i][j] << " ";

        cout << endl;

    }

}

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