creating new variable and making nested loop

Question

I have done all the code right and stuck with this silly thing: I cannot mange to stop the print when the previous generation is the same as the new...so when the prints pattern is the same as the previous pattern it should stop.

I need to copy the board before calling 'step' and then compare the new and copied boards, and only print if it has changed i need is to create a new variable just like i did board[], then to make a nested loop like the one in print, and inside do newboard[y][x] = board[y][x]

Please help me with this i cannot stop the print it always keep printing. please show me your syntax

void step(int board[][WIDTH], int rows) {
    int x, y;
    int neighbors[HEIGHT][WIDTH];
    for (y = 0; y < rows; y++)
        for (x = 0; x < WIDTH; x++)
            neighbors[y][x] = count_neighbors(board, rows, y, x);
    for (y = 0; y < rows; y++)
        for (x = 0; x < WIDTH; x++)
            if (board[y][x] == 1) { /* Currently alive */
                if (neighbors[y][x] < 2)
                    board[y][x] = 0; /* Death by boredom */
                else if (neighbors[y][x] > 3)
                    board[y][x] = 0; /* Death by overcrowding */
            }
            else { /* Currently empty */
                if (neighbors[y][x] == 3)
                    board[y][x] = 1;
            }
}

Maybe make step look for something changing, and return a boolean that you can use as the condition in your loop. — sje397
– sje397, Commented Jan 22, 2012 at 11:32

Mario · Accepted Answer · 2012-01-22 13:12:29Z

1

You just have to track changes. Rather trivial to do and far less work (execution/memory wise) than copying and comparing the whole array:

int step(int board[][WIDTH], int rows) { // now returns a bool
    int x, y; 
    int neighbors[HEIGHT][WIDTH]; 
    int changed = 0; // save changes
    for (y = 0; y < rows; y++) 
        for (x = 0; x < WIDTH; x++) 
            neighbors[y][x] = count_neighbors(board, rows, y, x); 
    for (y = 0; y < rows; y++) 
        for (x = 0; x < WIDTH; x++) 
            if (board[y][x] == 1) { /* Currently alive */ 
                if (neighbors[y][x] < 2) 
                {
                    board[y][x] = 0; /* Death by boredom */ 
                    changed = 1; // change happened
                }
                else if (neighbors[y][x] > 3) 
                {
                    board[y][x] = 0; /* Death by overcrowding */ 
                    changed = 1; // change happened
                }
            } 
            else { /* Currently empty */ 
                if (neighbors[y][x] == 3) 
                {
                    board[y][x] = 1; 
                    changed = 1; // change happened
                }
            } 
    return changed; // return the status (changed yes/no?)
} 

int main(void) {  
    int board[HEIGHT][WIDTH];  
    init(board, HEIGHT);  
    while (1) {  
        print(board, HEIGHT, WIDTH);
        if(step(board, HEIGHT) == 0) // no change
            break; // leave the loop
    }  
    return 0;  
}

Edit: If wanted, you could as well count the actual changes (instead of just saying yes/no) and return the number of changes. Could would stay almost the same.

edited Jan 22, 2012 at 13:12

answered Jan 22, 2012 at 11:32

Mario

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4 Comments

Blondy21 Over a year ago

errors on bool step(int board[][WIDTH], int rows) {: Error 2 error C2061: syntax error : identifier 'step' Error 4 error C2059: syntax error : 'type' Error 3 error C2059: syntax error : ';'

Mario Over a year ago

Ah, my mistake. Use int as return type. C doesn't know bool after all.

Jens Gustedt Over a year ago

@Mario, sure that C has bool (or _Bool) since C99.

Mario Over a year ago

Possible, but the classic one hasn't and I wouldn't assume it for now.

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