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Python Program to Print a given matrix in reverse spiral form

  • 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

 

 

Python3




# Python3 Code to Print a given  
# matrix in reverse spiral form
  
# This is a modified code of
# https:#www.geeksforgeeks.org/print-a-given-matrix-in-spiral-form/
R, C = 3, 6
  
def ReversespiralPrint(m, n, a):
  
    # Large array to initialize it
    # with elements of matrix
    b = [0 for i in range(100)]
  
    #/* k - starting row index
    #l - starting column index*/
    i, k, l = 0, 0, 0
  
    # Counter for single dimension array
    # in which elements will be stored
    z = 0
  
    # Total elements in matrix
    size = m * n
  
    while (k < m and l < n):
          
        # Variable to store value of matrix.
        val = 0
  
        # Print the first row 
        # from the remaining rows 
        for i in range(l, n):
              
            # printf("%d ", a[k][i])
            val = a[k][i]
            b[z] = val
            z += 1
        k += 1
  
        # Print the last column
        # from the remaining columns
        for i in range(k, m):
  
            # printf("%d ", a[i][n-1])
            val = a[i][n - 1]
            b[z] = val
            z += 1
  
        n -= 1
  
        # Print the last row 
        # from the remaining rows
        if (k < m):
            for i in range(n - 1, l - 1, -1):
                  
                # printf("%d ", a[m-1][i])
                val = a[m - 1][i]
                b[z] = val
                z += 1
  
        m -= 1
  
        # Print the first column 
        # from the remaining columns 
        if (l < n):
            for i in range(m - 1, k - 1, -1):
                  
                # printf("%d ", a[i][l])
                val = a[i][l]
                b[z] = val
                z += 1
            l += 1
  
    for i in range(size - 1, -1, -1):
        print(b[i], end = " ")
  
# Driver Code
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 mohit kumar

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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