Contain Virus

Similar Problems:

- Tag: #graph

A virus is spreading rapidly, and your task is to quarantine the infected area by installing walls.

The world is modeled as a 2-D array of cells, where 0 represents uninfected cells, and 1 represents cells contaminated with the virus. A wall (and only one wall) can be installed between any two 4-directionally adjacent cells, on the shared boundary.

Every night, the virus spreads to all neighboring cells in all four directions unless blocked by a wall. Resources are limited. Each day, you can install walls around only one region — the affected area (continuous block of infected cells) that threatens the most uninfected cells the following night. There will never be a tie.

Can you save the day? If so, what is the number of walls required? If not, and the world becomes fully infected, return the number of walls used.

Example 1:

Input: grid = [[0,1,0,0,0,0,0,1], [0,1,0,0,0,0,0,1], [0,0,0,0,0,0,0,1], [0,0,0,0,0,0,0,0]] Output: 10 Explanation: There are 2 contaminated regions. On the first day, add 5 walls to quarantine the viral region on the left. The board after the virus spreads is: [[0,1,0,0,0,0,1,1], [0,1,0,0,0,0,1,1], [0,0,0,0,0,0,1,1], [0,0,0,0,0,0,0,1]] On the second day, add 5 walls to quarantine the viral region on the right. The virus is fully contained.

Example 2:

Input: grid = [[1,1,1], [1,0,1], [1,1,1]] Output: 4 Explanation: Even though there is only one cell saved, there are 4 walls built. Notice that walls are only built on the shared boundary of two different cells.

Example 3:

Input: grid = [[1,1,1,0,0,0,0,0,0], [1,0,1,0,1,1,1,1,1], [1,1,1,0,0,0,0,0,0]] Output: 13 Explanation: The region on the left only builds two new walls.

Note:

- The number of rows and columns of grid will each be in the range [1, 50].
- Each grid[i][j] will be either 0 or 1.
- Throughout the described process, there is always a contiguous viral region that will infect strictly more uncontaminated squares in the next round.

Github: code.dennyzhang.com

Credits To: leetcode.com

Leave me comments, if you have better ways to solve.

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