Question

我编写了一个方法来填充由m x n矩阵表示的位图。我想要做的是将初始像素推入堆栈，然后在while循环中弹出堆栈中的元素，为其着色并推送相邻像素（如果它们与初始像素的初始颜色相同）。

public void fill(int x, int y, char c) {
    char tempColor = this.bitmap[y - 1][x - 1];
    Point currentPoint;

    Stack<Point> fillStack = new Stack<Point>();

    fillStack.push(new Point(x, y));

    do {
        currentPoint = fillStack.pop();
//      System.out.println(currentPoint.x + " " + currentPoint.y);
//      System.out.println("Current state of the stack:");
//      for (Point p: fillStack)
//          System.out.println(p.x + " " + p.y);
        this.bitmap[currentPoint.y - 1][currentPoint.x - 1] = c;
        if (currentPoint.y - 1 > 0 && this.bitmap[currentPoint.y - 2][currentPoint.x - 1] == tempColor) {
            fillStack.push(new Point(x, y - 1));
//          System.out.println("Pushing " + currentPoint.x + " " + (currentPoint.y - 1));
        }
        if (currentPoint.y - 1 < n - 1 && this.bitmap[currentPoint.y][currentPoint.x - 1] == tempColor) {
            fillStack.push(new Point(x, y + 1));
//          System.out.println("Pushing " + currentPoint.x + " " + (currentPoint.y + 1));
        }
        if (currentPoint.x - 1 > 0 && this.bitmap[currentPoint.y - 1][currentPoint.x - 2] == tempColor) {
            fillStack.push(new Point(x - 1, y));
//          System.out.println("Pushing " + (currentPoint.x - 1) + " " + currentPoint.y);
        }
        if (currentPoint.x - 1 < m - 1 && this.bitmap[currentPoint.y - 1][currentPoint.x] == tempColor) {
            fillStack.push(new Point(x + 1, y));    
//          System.out.println("Pushing " + (currentPoint.x + 1) + " " + currentPoint.y);
            }
        } while (!fillStack.isEmpty());
    }
}

但它不能起作用我似乎无法发现的原因。输出（未注释的调试行）如下：

3 3
Current state of the stack:
Pushing 3 2
Pushing 3 4
Pushing 4 3
4 3
Current state of the stack:
3 2
3 4
Pushing 4 2
Pushing 4 4
Pushing 5 3
4 3
Current state of the stack:
3 2
3 4
3 2
3 4
Pushing 4 2
Pushing 4 4
Pushing 5 3
4 3
Current state of the stack:
3 2
3 4
3 2
3 4
3 2
3 4
Pushing 4 2
Pushing 4 4
Pushing 5 3
4 3
Current state of the stack:
3 2
3 4
3 2
3 4
3 2
3 4
3 2
3 4
Pushing 4 2
Pushing 4 4
Pushing 5 3
4 3
Current state of the stack:
3 2
3 4
3 2
3 4
3 2
3 4
3 2
3 4
3 2
3 4
Pushing 4 2
Pushing 4 4
Pushing 5 3
4 3
Current state of the stack:
3 2
3 4
3 2
3 4
3 2
3 4
3 2
3 4
3 2
3 4
3 2
3 4
Pushing 4 2
Pushing 4 4
Pushing 5 3
4 3
Current state of the stack:
3 2
3 4
3 2
3 4
3 2
3 4
3 2
3 4
3 2
3 4
3 2
3 4
3 2
3 4
Pushing 4 2
Pushing 4 4
Pushing 5 3
4 3
Current state of the stack:
3 2
3 4
3 2
3 4
3 2
3 4
3 2
3 4
3 2
3 4
3 2
3 4
3 2
3 4
3 2
3 4
Pushing 4 2
Pushing 4 4
Pushing 5 3
4 3
Current state of the stack:
3 2
3 4
3 2
3 4
3 2
3 4
3 2
3 4
3 2
3 4
3 2
3 4
3 2
3 4
3 2
3 4
3 2
3 4

......它在无休止的循环中继续这样。可能是什么问题？

Answer 1

你的打印声明说一件事，你的代码又做了另一件事！ ;）

例如：

fillStack.push(new Point(x, y - 1));
System.out.println("Pushing " + currentPoint.x + " " + (currentPoint.y - 1));

看看你是否能发现差异......

堆栈不断弹出相同的元素

1 个答案: