check50 说 CS50 过滤器-更多边缘不正确吗？

Question

// Detect edges
void edges(int height, int width, RGBTRIPLE image[height][width])
{
    // Copying
    RGBTRIPLE copy[height][width];
    for (int i = 0; i < height; i++)
    {
        for (int j = 0; j < width; j++)
        {
            copy[i][j] = image[i][j];
        }
    }

    int Gx[3][3] = {{-1, 0, 1}, {-2, 0, 2}, {-1, 0, 1}};
    int Gy[3][3] = {{-1, -2, -1}, {0, 0, 0}, {1, 2, 1}};

    for (int i = 0; i < height; i++)
    {
        for (int j = 0; j < width; j++)
        {
            int GxsumRed = 0;
            int GxsumGreen = 0;
            int GxsumBlue = 0;

            int GysumRed = 0;
            int GysumGreen = 0;
            int GysumBlue = 0;

            // Forming 3x3 grid
            int m = 0;  // For Gx and Gy
            for (int k = i - 1; k < i + 2; k++)
            {
                if (k < 0)
                {
                    continue;
                }

                // if k > height then break
                if (k >= height)
                {
                    break;
                }
                int n = 0;  // For Gx and Gy
                for (int l = j - 1; l < j + 2; l++)
                {
                    if (l < 0)
                    {
                        continue;
                    }
                    if (l >= width)
                    {
                        break;
                    }

                    GxsumRed += Gx[m][n] * copy[k][l].rgbtRed;
                    GxsumGreen += Gx[m][n] * copy[k][l].rgbtGreen;
                    GxsumBlue += Gx[m][n] * copy[k][l].rgbtBlue;

                    GysumRed += Gy[m][n] * copy[k][l].rgbtRed;
                    GysumGreen += Gy[m][n] * copy[k][l].rgbtGreen;
                    GysumBlue += Gy[m][n] * copy[k][l].rgbtBlue;
                    n++;
                }
                m++;
            }

            int newRed = round(sqrt((GxsumRed * GxsumRed) + (GysumRed * GysumRed)));
            int newGreen = round(sqrt((GxsumGreen * GxsumGreen) + (GysumGreen * GysumGreen)));
            int newBlue = round(sqrt((GxsumBlue * GxsumBlue) + (GysumBlue * GysumBlue)));

            // Caping to 255
            if (newRed > 255)
            {
                newRed = 255;
            }

            if (newGreen > 255)
            {
                newGreen = 255;
            }

            if (newBlue > 255)
            {
                newBlue = 255;
            }

            image[i][j].rgbtRed = newRed;
            image[i][j].rgbtGreen = newGreen;
            image[i][j].rgbtBlue = newBlue;
        }
    }
    return;
}

此 CS50 问题集 4. 筛选更多问题。除了边缘功能之外，一切都很好。 ChatGPT 说我的代码是正确的，但 check50 说它不正确，为什么？ 我做错了什么？

请问有人可以告诉我吗？拜托拜托？

这是所有详细信息:

Answer 1

问题是你增加 n和m在循环体的末尾，但是当 k < 0 时此增量被绕过或l < 0分别为 true 和 continue语句已被评估。

您应该避免 continue语句或将增量移至 for 的第三个子句声明。

尽早脱离循环 if k >= height或l >= width是一种优化，它打破了代码的对称性，并使编译器更难以展开或并行化循环。即使对于中等大小的图像，这种优化也是微不足道的。建议优先考虑代码的可读性和规律性，而不是过早的优化。

这是内部循环的修改版本:

            // Forming 3x3 grid
            for (int m = 0; m < 3; m++)
            {
                int k = i - 1 + m;
                if (k >= 0 && k < height)
                {
                    for (int n = 0; n < 3; n++)
                    {
                        int l = j - 1 + n;
                        if (l >= 0 && l < width)
                        {
                            GxsumRed   += Gx[m][n] * copy[k][l].rgbtRed;
                            GxsumGreen += Gx[m][n] * copy[k][l].rgbtGreen;
                            GxsumBlue  += Gx[m][n] * copy[k][l].rgbtBlue;

                            GysumRed   += Gy[m][n] * copy[k][l].rgbtRed;
                            GysumGreen += Gy[m][n] * copy[k][l].rgbtGreen;
                            GysumBlue  += Gy[m][n] * copy[k][l].rgbtBlue;
                        }
                    }
                }
            }