1568 - Minimum Number of Days to Disconnect Island.

Hard

You are given an m x n binary grid grid where 1 represents land and 0 represents water. An island is a maximal 4-directionally (horizontal or vertical) connected group of 1's.

The grid is said to be connected if we have exactly one island , otherwise is said disconnected.

In one day, we are allowed to change any single land cell (1) into a water cell (0).

Return the minimum number of days to disconnect the grid.

Example 1:

Input: grid = \[\[0,1,1,0],0,1,1,0,0,0,0,0]

Output: 2

Explanation: We need at least 2 days to get a disconnected grid. Change land grid1 and grid2 to water and get 2 disconnected island.

Example 2:

Input: grid = \[\[1,1]]

Output: 2

Explanation: Grid of full water is also disconnected ([1,1] -> [0,0]), 0 islands.

Constraints:

• m == grid.length

• n == grid[i].length

• 1 <= m, n <= 30

• grid[i][j] is either 0 or 1.