Count Land Components Enclosed Away From the Boundary

### Problem In grid, 0 means land and 1 means water. An island is a maximal group of land cells joined horizontally or vertically. Count the islands completely surrounded by water on all four sides, so none of their cells touches the grid boundary. ```cpp class Solution { public: int closedIsland(vector<vector<int>>& grid); }; ``` ### Examples **Example 1:** ```text Input: grid = [[1,1,1],[1,0,1],[1,1,1]] Output: 1 Explanation: The center land cell is enclosed on all four sides. ``` **Example 2:** ```text Input: grid = [[1,0,1],[1,0,1],[1,1,1]] Output: 0 Explanation: The center land is connected to the top boundary, so its island is not closed. ``` ### Constraints - Each grid dimension is between 1 and 100. - Every entry is 0 or 1. ### Contract considerations Land is 0 here, not 1. Every boundary, rather than only corners, must be checked. ```hint Read the boundary condition Do diagonal land cells belong to the same island, and can land touching any outer edge qualify? ``` ### Boundary reminders Land is 0 here, not 1. Every boundary, rather than only corners, must be checked.