Number of Closed Islands

Given a 2D `grid` consists of `0s` (land) and `1s` (water).  An _island_ is a maximal 4-directionally connected group of `0s` and a _closed island_ is an island **totally** (all left, top, right, bottom) surrounded by `1s.` Return the number of _closed islands_.   **Example 1:** **Input:** 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]] **Output:** 2 **Explanation:** Islands in gray are closed because they are completely surrounded by water (group of 1s). ``` **Example 2:** **Input:** grid = [[0,0,1,0,0],[0,1,0,1,0],[0,1,1,1,0]] **Output:** 1 ``` **Example 3:** **Input:** 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]] **Output:** 2 ```   **Constraints:** - `1 <= grid.length, grid[0].length <= 100` - `0 <= grid[i][j] <=1`