Print a given matrix in reverse spiral form

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

C++

 // This is a modified code of // https://www.geeksforgeeks.org/print-a-given-matrix-in-spiral-form/ #include #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;            /* 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<

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;                     /* 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;                    /* 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

 = \$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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