if (m_mark[y * m_width + x + 1] < 0 || m_mark[y * m_width + x - 1] < 0 || m_mark[(y + 1) * m_width + x] < 0 || m_mark[(y - 1) * m_width + x] < 0) continue;如上,我已经知道索引可能会超出数组边界,然后怎么规避这个问题?