Print n x n spiral matrix using O(1) extra space - GeeksforGeeks

Print n x n spiral matrix using O(1) extra space - GeeksforGeeks
Given a number n, print a n x n spiral matrix (of numbers from 1 to n x n) in clockwise direction using O(1) space.

The solution becomes simple if extra space is allowed. We allocate memory for n x n matrix and for every element starting from n*n to 1, we start filling out matrix in spiral order. To maintain the spiral order four loops are used, each for top, right, bottom and left corner of the matrix.

void printSpiral(int n)

{

    for (int i = 0; i < n; i++)

    {

        for (int j = 0; j < n; j++)

        {

            // x stores the layer in which (i, j)th

            // element lies

            int x;

 

            // Finds minimum of four inputs

            x = min(min(i, j), min(n-1-i, n-1-j));

 

            // For upper right half

            if (i <= j)

                printf("%2d ", (n-2*x)*(n-2*x) - (i-x)

                       - (j-x));

 

            // for lower left half

            else

                printf("%2d ", (n-2*x-2)*(n-2*x-2) + (i-x)

                       + (j-x));

        }

        printf("\n");

    }

}

For a given number n, print a n x n spiral matrix in counter clockwise direction using O(1) space.

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