Getting the adjacent elements of a 2D matrix (depth one only)

Question

I have an 800 by 600 image. I want to treat it like a matrix and get the adjacent elements

ex.

(0,0) (1,0) (2,0) (3,0)

(0,1) (1,1) (2,1) (3,1)

(0,2) (1,2) (2,2) (3,2)

(0,3) (1,3) (2,3) (3,3)

example solutions: (0,0) is adjacent to: (1,0) (0,1) (1,1)

(1,1) is adjacent to: (0,0) (1,0) (2,0) (2,1) (2,2) (1,2) (0,2) (0,1)

so I have written a struct array that i will store each one of these points into

typdef struct point
{
    int x;
    int y;
}point[800*600];

so my first idea was to implement a dfs but that did not really work out so I wanted to get an outside opinion to keep myself on the right track. thanks

It seems like you're overthinking this problem - why not just use a 2D array? — Carl Norum
What do you mean by "store each one of these points"? What are you storing? color values? — Rumple Stiltskin
imagine you have arr an object of type point. What would there be in arr[0].x? And in arr[0].y? And in arr[800].x? ... — pmg

oosterwal oosterwal · Accepted Answer · 2011-03-31T18:58:37

The final answer depends on how you visualize the arrangement of your 2D display into the 1D array ('row-first column-last' or 'column-first row-last').

Assuming 'row-first' (pixels along the row increment by 1, pixels along the column increment by ROW_LENGTH):

First use some definitions to set values for ROW_LENGTH and COL_LENGTH

#define ROW_LENGTH 800
#define COL_LENGTH 600

Then you can easily adjust your size if needs change without affecting how the rest of the code works.

typdef struct point
{
    int x;
    int y;
}point[ROW_LENGTH*COL_LENGTH];

Later, adjacent points can be obtained with something like:

adjacentWest = point[(y*ROW_LENGTH) + (x-1)];
adjacentNorth = point[((y+1)*ROW_LENGTH) + x];

You'll need to adjust North and South to be +1 or -1 depending on if your origin is in the top-left or bottom-left of your display.

Getting the adjacent elements of a 2D matrix (depth one only)

1 Answers