public class Solution
extends Object
1254 - Number of Closed Islands\.
Medium
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`