Crocus - 5 days ago 4x

C Question

I've got an assignment to recreate Conway's Game Of Life in C. In the following code I'm trying to check if the neighbors to a given coordinate in a 2D-array has the status DEAD or ALIVE:

`int checkNeighbor(int i, int j, cell field[i][j]) {`

int sum=0;

if(canGoUp(i) && canGoLeft(j) && (field[i-1][j-1].current == ALIVE)) {

sum++;

}

if(canGoUp(i) && (field[i-1][j].current == ALIVE)) {

sum++;

}

if(canGoUp(i) && canGoRight(j) && (field[i-1][j+1].current == ALIVE)) {

sum++;

}

if(canGoRight(j) && (field[i][j+1].current == ALIVE)) {

sum++;

}

if(canGoDown(i) && canGoRight(j) && (field[i+1][j+1].current == ALIVE)) {

sum++;

}

if(canGoDown(i) && (field[i+1][j].current == ALIVE)) {

sum++;

}

if(canGoDown(i) && canGoLeft(j) && (field[i+1][j-1].current == ALIVE)) {

sum++;

}

if(canGoLeft(j) && (field[i][j-1].current == ALIVE)) {

sum++;

}

return sum;

}

The functions named "canGoUP" or "canGoDown" etc prevents segfaults by checking if the coordinate is near the edge of the 2D-array. Now, For some reason the code is not working nearly perfect. I get some indications of neighbors but it almost never tells me the right amount. Is there a better way to go about the problem? or have I just missed something in the code?

Answer

This function is mistaken about how large the `field`

matrix is. It believes `field`

has `i`

rows and `j`

columns. That however is not correct. It likely has some larger number of rows and columns.

For example, if you call this function with `i==0`

and `j==0`

, the array declaration for that call is `cell field[0][0]`

, i.e. an empty array which is not valid.

You need to pass in the actual dimensions as additional parameters and use those for the array size.

```
int checkNeighbor(int i, int j, int rows, int cols, cell field[rows][cols]);
```

Source (Stackoverflow)

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