Array in spiral order

pratikasthana17 · #1 16-Sep-2009, 02:49

Your program should print the contents of a 2-dimensional array in spiral order. Suppose your array is
1 2 3 4 5 6
7 8 9 10 11 12
13 14 15 16 17 18
19 20 21 22 23 24
The output should be:
1 2 3 4 5 6 12 18 24 23 22 21 20 19 13 7 8 9 10 11 17 16 15 14
Your program should take m and n as inputs, where m and n specify the dimensions of the array. Once the user inputs m and n, the program should initialize the array with random numbers using the rand() function.
Once the array is initialized, print the actual contents of the array. Then, compute and print the array in spiral order.

ocicat · #2 16-Sep-2009, 06:20

Quote:

Originally Posted by pratikasthana17

Your program should print the contents of a 2-dimensional array in spiral order.

This is the third post you have made which simply states a problem without showing any attempt at solution. See my following response:

http://www.gidforums.com/showpost.ph...02&postcount=2

fakepoo · #3 17-Sep-2009, 15:01

The way that I would do it is:

Declare an array of the exact same size as your 2D array and fill it with zeros. I will call it Map.
Declare a variable to keep track of your direction.
Set the starting conditions: Position is 0,0 and direction is RIGHT.
Print the value at the current position and set the value of the same position of Map to a 1.
If the next position (depending on the direction) of Map is a 1 or if it is outside the bounds of the array, change the direction.
If the next position (depending on the direction) of Map is a 1 or if it is outside the bounds of the array, you are done.
Set position to the next position.
Repeat steps 4-7 until done.

Mexican Bob · #4 18-Sep-2009, 09:38

Quote:

Originally Posted by pratikasthana17

Your program should print the contents of a 2-dimensional array in spiral order. Suppose your array is
1 2 3 4 5 6
7 8 9 10 11 12
13 14 15 16 17 18
19 20 21 22 23 24
The output should be:
1 2 3 4 5 6 12 18 24 23 22 21 20 19 13 7 8 9 10 11 17 16 15 14
Your program should take m and n as inputs, where m and n specify the dimensions of the array. Once the user inputs m and n, the program should initialize the array with random numbers using the rand() function.
Once the array is initialized, print the actual contents of the array. Then, compute and print the array in spiral order.

Here is a solution that works for square dimensions for your array. I'll leave it to you to decide how to implement m != n dimensioned array spiral printing.

You may want to consider fakepoo's "Map" strategy, though. Only twice the storage and processing!

CPP / C++ / C Code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

void print_array(const int** pp, const size_t m, const size_t n)
{
    size_t i, j;
    if(m > 0 && n > 0 && pp != NULL)
    {
        for(i = 0; i < m; i++)
        {
            for(j = 0; j < n; j++)
            {
                printf("%4d ", pp[i][j]);
            }
            printf("\n");
        } 
    }
}

void print_spiral(const int** pp, const size_t m, const size_t n)
{
    size_t i, j, k;
    if(m == n && n > 0 && pp != NULL)
    {
        for(i = (m-1), j = 0; i > 0; i--, j++)
        {
            for(k = j; k < i; k++)
            {
                printf("%4d ", pp[j][k]);
            }
            for(k = j; k < i; k++)
            {
                printf("%4d ", pp[k][i]);
            }
            for(k = i; k > j; k--)
            {
                printf("%4d ", pp[i][k]);
            }
            for(k = i; k > j; k--)
            {
                printf("%4d ", pp[k][j]);
            }
        }
        if(m % 2 == 1)
        {
            printf("%4d ", pp[(m-1)/2][(m-1)/2]);
        }
        printf("\n");
    }
}

int main()
{
    int     i;
    int     j;
    int     m;
    int     n;
    int**   pp;
    int     r;

#ifdef I_WANT_TO_SEE_RECOGNIZABLE_VALUES
    int     d = 1;
#endif

    printf("Enter 'm' dimension: ");
    scanf("%d", &m);

    printf("Enter 'n' dimension: ");
    scanf("%d", &n);

    r = m * n * 100;

    if(r > 1)
    {
        srand((unsigned)time(0));
        pp = (int**)malloc(sizeof(int*) * m);
        if(pp != NULL)
        {
            for(i = 0; i < m; i++)
            {
                pp[i] = (int*)malloc(sizeof(int) * n);
                for(j = 0; j < n; j++)
                {
#ifdef I_WANT_TO_SEE_RECOGNIZABLE_VALUES
                    pp[i][j] = d++;
#else
                    pp[i][j] = 1 + (int)(r * (rand() / (RAND_MAX + 1.0)));
#endif
                }
            }
        }
        print_array((const int**)pp, m, n);
        printf("\n\n");
        if(m == n)
        {
            print_spiral((const int**)pp, m, n);
        }

        for(i = 0; i < m; i++)
        {
            free(pp[i]);
        }
        free(pp);
    }
    return 0;
}

Output:

Code:


// with I_WANT_TO_SEE_RECOGNIZABLE_VALUES defined

$ ./prati 
Enter 'm' dimension: 5
Enter 'n' dimension: 5
   1    2    3    4    5 
   6    7    8    9   10 
  11   12   13   14   15 
  16   17   18   19   20 
  21   22   23   24   25 


   1    2    3    4    5   10   15   20   25   24   23   22   21   16   11    6    7    8    9   14   19   18   17   12   13 

// without I_WANT_TO_SEE_RECOGNIZABLE_VALUES defined

$ ./prati 
Enter 'm' dimension: 4
Enter 'n' dimension: 4
 172  619  568  405 
1054  944  291  618 
 845 1450  409  459 
1265   11  594  525 


 172  619  568  405  618  459  525  594   11 1265  845 1054  944  291  409 1450

MxB

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Array in spiral order

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Re: Array in spiral order

Re: Array in spiral order