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Java Program to Print a given matrix in reverse spiral form

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  • Last Updated : 10 Jan, 2022

Given a 2D array, print it in reverse spiral form. We have already discussed Print a given matrix in spiral form. This article discusses how to do the reverse printing. See the following examples. 
 

Input:
        1    2   3   4
        5    6   7   8
        9   10  11  12
        13  14  15  16
Output: 
10 11 7 6 5 9 13 14 15 16 12 8 4 3 2 1
Input:
        1   2   3   4  5   6
        7   8   9  10  11  12
        13  14  15 16  17  18
Output: 
11 10 9 8 7 13 14 15 16 17 18 12 6 5 4 3 2 1

 

 

Java




// JAVA Code for Print a given matrix in 
// reverse spiral form
class GFG {
  
    public static int R = 3, C = 6;
      
    // Function that print matrix in reverse spiral form.
    public static void ReversespiralPrint(int m, int n,
                                             int a[][])
    {
        // Large array to initialize it
        // with elements of matrix
        long b[] = new long[100];
           
        /* k - starting row index
        l - starting column index*/
        int i, k = 0, l = 0;
           
        // Counter for single dimension array
        //in which elements will be stored
        int z = 0;
           
        // Total elements in matrix
        int size = m * n;
       
        while (k < m && l < n)
        {
            // Variable to store value of matrix.
            int val;
               
            /* Print the first row from the remaining 
            rows */
            for (i = l; i < n; ++i)
            {
                  
                val = a[k][i];
                b[z] = val;
                ++z;
            }
            k++;
       
            /* Print the last column from the remaining
            columns */
            for (i = k; i < m; ++i)
            {
                  
                val = a[i][n-1];
                b[z] = val;
                ++z;
            }
            n--;
       
            /* Print the last row from the remaining 
            rows */
            if ( k < m)
            {
                for (i = n-1; i >= l; --i)
                {
                      
                    val = a[m-1][i];
                    b[z] = val;
                    ++z;
                }
                m--;
            }
       
            /* Print the first column from the remaining 
            columns */
            if (l < n)
            {
                for (i = m-1; i >= k; --i)
                {
                      
                    val = a[i][l];
                    b[z] = val;
                    ++z;
                }
                l++;
            }
        }
          
        for (int x = size-1 ; x>=0 ; --x)
        {
            System.out.print(b[x]+" ");
        }
    }    
      
    /* Driver program to test above function */
    public static void main(String[] args) 
    {
        int a[][] = { {1, 2, 3, 4, 5, 6},
                    {7, 8, 9, 10, 11, 12},
                    {13, 14, 15, 16, 17, 18}};
          
        ReversespiralPrint(R, C, a);
         
    }
  }
// This code is contributed by Arnav Kr. Mandal.

Output: 

11 10 9 8 7 13 14 15 16 17 18 12 6 5 4 3 2 1

Please refer complete article on Print a given matrix in reverse spiral form for more details!


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