更改动态2D布尔数组中的一个值似乎会更改其他数组中不同位置的值

Question

I have two dynamically allocated boolean arrays of size height * width, that I allocated / initialized with...

bool ** visited; 
bool ** inQueue; 
visited = new bool * [height];
inQueue = new bool * [height];
for (int i = 0; i < height; i++) {
    visited[i] = new bool(width);
    inQueue[i] = new bool(width);
}

for (int i = 0; i < height; i++)
    for (int j = 0; j < width; j++) {
        visited[i][j] = false;
        inQueue[i][j] = false;
    }

And at the end of my program I clear up that memory with...

for (int i = 0; i < height; i++) {
    delete [] visited[i];
    delete [] inQueue[i];
}
delete [] visited;
delete [] inQueue;

But, in between, I get a weird condition where various values in visited's 0th column become true even though they are not being directly changed.

An example of this behavior is:

. . . . . . . . . . . X . . . . .       0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 
    . . . . . . # . # . X X X . # . .       0 0 0 0 0 0 1 0 1 0 1 1 1 0 1 0 0 
    . . . . . . # . . # X X X X # . .       0 0 0 0 0 0 1 0 0 1 1 1 1 1 1 0 0 
    . . . . . . # . X X X X X X # . .       0 0 0 0 0 0 1 0 1 1 1 1 1 1 1 0 0 
    . . . . . . # # # # # X X X # . .       0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 0 0 
    . # . . . . . . . . # X X X X @ .       0 1 0 0 0 0 0 0 0 0 1 1 1 1 1 0 0 
    . # . . . . . . . . # X X X X . .        
    . # . . . . . . . . # X X X . . .       0 1 0 0 0 0 0 0 0 0 1 1 1 1 0 0 0 
    . G # . . . # # # . # X X . # . .       0 0 1 0 0 0 1 1 1 0 1 1 1 0 1 0 0 
    . # . . . . . . . . . X . . . . .       0 1 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 
    . . . . . . . . . . # . . . . . .       0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 
    . . . . . . . . . . . . . . . . .       0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 
    . . . . . . . . . . . . . . . . .       0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 
    . . . . . . . . . . . . . . . . .       0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 
    . . . . . . # . . . . . . . # . .       0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 
    . . . . . . # . . . . . . . # . .       0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 
    . . . . . . # . . . . . . . # . .       0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 

    [6][0] @ 205: 0
    
    [6][0] @ 210: 1
    ...

This is my output. As you can see, the position in visited[6][0] becomes true on what I've labeled in my output after line 205, while adding the eastern position. That code for that change is here:

cout << "[6][0] @ 205: " << visited[6][0] << endl;
cout << "Added Eastern Pos: (" << (east % width) << ", " << (int)floor(east / width) << ")\n";
inQueue[(int)floor(east / width)][east % width] = true;
cout << "[6][0] @ 208: " << visited[6][0] << endl;
xVal.addToQueue(to_string(east % width));

Specifically on the third line I change the value of inQueue, and then immediately afterwards (as seen in the block above) visited[6][0] has changed to true. Keep in mind that

(int)floor(east / width)

is actually 5, and

east % width

is 16. So, to me it makes no sense whatsoever that visited would be changed. This happens incrementally throughout my programs run, always with values of the 0th column being changed.

Any ideas?

Answer 1

With visited[i] = new bool(width) , you allocate a single boolean value, not an array of booleans. Henceforth, when expecting an array of width elements, which actually consists only of one, you exceed array bounds and get undefined behaviour (and that's what you see in your output).

See the difference:

int main() {
    int width =20;
    int sizeofBool = sizeof(bool(width)); // -> 1
    int sizeOfBoolArray = sizeof(bool[width]); // -> 20
}

So write visited[i] = new bool[width] (and also for inQueue ), and you should at least get ahead.