C语言 - 读取方阵的一般算法，基于它的平方数？

So we're reading a matrix and saving it in an array sequentially. We read the matrix from a starting [x,y] point which is provided. Here's an example of some code I wrote to get the values of [x-1,y] [x+1,y] [x,y-1] [x,y+1], which is a cross. So we're reading a matrix and saving it in an a