<p>二维矩阵 <code>grid</code> 由 <code>0</code> (土地)和 <code>1</code> (水)组成。岛是由最大的4个方向连通的 <code>0</code> 组成的群,封闭岛是一个 <code>完全</code> 由1包围(左、上、右、下)的岛。</p> <p>请返回 <em>封闭岛屿</em> 的数目。</p> <p> </p> <p><strong>示例 1:</strong></p> <p><img alt="" src="https://assets.leetcode.com/uploads/2019/10/31/sample_3_1610.png" style="height: 151px; width: 240px;" /></p> <pre> <strong>输入:</strong>grid = [[1,1,1,1,1,1,1,0],[1,0,0,0,0,1,1,0],[1,0,1,0,1,1,1,0],[1,0,0,0,0,1,0,1],[1,1,1,1,1,1,1,0]] <strong>输出:</strong>2 <strong>解释:</strong> 灰色区域的岛屿是封闭岛屿,因为这座岛屿完全被水域包围(即被 1 区域包围)。</pre> <p><strong>示例 2:</strong></p> <p><img src="https://assets.leetcode-cn.com/aliyun-lc-upload/uploads/2019/11/07/sample_4_1610.png" style="height: 98px; width: 160px;" /></p> <pre> <strong>输入:</strong>grid = [[0,0,1,0,0],[0,1,0,1,0],[0,1,1,1,0]] <strong>输出:</strong>1 </pre> <p><strong>示例 3:</strong></p> <pre> <strong>输入:</strong>grid = [[1,1,1,1,1,1,1], [1,0,0,0,0,0,1], [1,0,1,1,1,0,1], [1,0,1,0,1,0,1], [1,0,1,1,1,0,1], [1,0,0,0,0,0,1], [1,1,1,1,1,1,1]] <strong>输出:</strong>2 </pre> <p> </p> <p><strong>提示:</strong></p> <ul> <li><code>1 <= grid.length, grid[0].length <= 100</code></li> <li><code>0 <= grid[i][j] <=1</code></li> </ul>