How to count number of neighbors in a matrix?

Question

Okay so I am making the game of life in C and I can't figure out how to count the neighbors from the matrix..

Here is my current code

http://pastebin.com/8fTdbpfs

Sorry I think it just looks better on pastebin.

Answer 1

For cell at location (i,j), i.e. i row, j column, coordinates of all its eight neighbors are

(i-1,j-1) | (i-1,j) | (i-1,j+1)
----------+---------+----------
(i,  j-1) | (i  ,j) | (i  ,j+1)
----------+---------+----------
(i+1,j-1) | (i+1,j) | (i+1,j+1)

In a two-dimensional array array[row][col], you could access them by array[i][j]. Of course, you need to make sure every coordinates are valid before you try to access cell at that coordinate, you can using the following condition to make this check:

// for coordinate (i, j) in array[row][col]
if ((0 <= i) && (i < row) && (0 <= j) && (j < col)) {
    /* access array[i][j] */
}