Print a given matrix in reverse spiral form

Difficulty Level : Medium
Last Updated : 03 Apr, 2019

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

Recommended: Please solve it on “PRACTICE” first, before moving on to the solution.

C++

// This is a modified code of 
// https://www.geeksforgeeks.org/print-a-given-matrix-in-spiral-form/ 
#include <iostream> 
#define R 3 
#define C 6 
using namespace std; 
  
// Function that print matrix in reverse spiral form. 
void ReversespiralPrint(int m, int n, int a[R][C]) 
{ 
    // Large array to initialize it 
    // with elements of matrix 
    long int b[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) 
        { 
            // printf("%d ", a[k][i]); 
            val = a[k][i]; 
            b[z] = val; 
            ++z; 
        } 
        k++; 
  
        /* Print the last column from the remaining columns */
        for (i = k; i < m; ++i) 
        { 
            // printf("%d ", a[i][n-1]); 
            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) 
            { 
                // printf("%d ", a[m-1][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) 
            { 
                // printf("%d ", a[i][l]); 
                val = a[i][l]; 
                b[z] = val; 
                ++z; 
            } 
            l++; 
        } 
    } 
    for (int i=size-1 ; i>=0 ; --i) 
    { 
        cout<<b[i]<<" "; 
    } 
} 
  
/* Driver program to test above functions */
int main() 
{ 
    int a[R][C] = { {1, 2, 3, 4, 5, 6}, 
                    {7, 8, 9, 10, 11, 12}, 
                    {13, 14, 15, 16, 17, 18}}; 
    ReversespiralPrint(R, C, a); 
    return 0; 
} 

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. 

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 

C#

// C# Code for Print a given matrix in  
// reverse spiral form 
using System; 
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) 
        { 
        Console.Write(b[x]+" "); 
        } 
    }  
      
    /* Driver program to test above function */
    public static void Main()  
    { 
        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 vt_m. 

PHP

<?php 
// PHP Code for Print a given   
// matrix in reverse spiral form 
$R=3; 
$C=6; 
  
// Function that print matrix  
// in reverse spiral form. 
function ReversespiralPrint($m, $n, array $a) 
{ 
      
    // Large array to initialize it 
    // with elements of matrix 
    $b; 
      
    // k - starting row index 
    // l - starting column index 
    $k = 0; 
    $l = 0; 
      
    // Counter for single dimension array 
    // in which elements will be stored 
    $z = 0; 
      
    // Total elements in matrix 
    $size = $m*$n; 
  
    while ($k < $m && $l < $n) 
    { 
          
        // Variable to store 
        // value of matrix. 
        $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) 
        { 
              
            // printf("%d ", a[i][n-1]); 
            $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) 
            { 
                  
                // printf("%d ", a[m-1][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; 
            } 
            $l++; 
        } 
    } 
    for ($i = $size - 1; $i >= 0; --$i) 
    { 
        echo $b[$i]." "; 
    } 
} 
  
    // Driver Code 
    $a= array(array(1, 2, 3, 4, 5, 6), 
              array(7, 8, 9, 10, 11, 12), 
              array(13, 14, 15, 16, 17, 18)); 
    ReversespiralPrint($R, $C, $a); 
  
// This Code is contributed by mits  
?> 

Output:

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

This article is contributed by Sahil Rajput. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

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Recommended: Please solve it on “PRACTICE” first, before moving on to the solution.

C++

Java

Python3

C#

PHP