2257. Count Unguarded Cells in the Grid

Medium

356

33

You are given two integers `m`

and `n`

representing a **0-indexed** `m x n`

grid. You are also given two 2D integer arrays `guards`

and `walls`

where `guards[i] = [row`

and _{i}, col_{i}]`walls[j] = [row`

represent the positions of the _{j}, col_{j}]`i`

guard and ^{th}`j`

wall respectively.^{th}

A guard can see **every** cell in the four cardinal directions (north, east, south, or west) starting from their position unless **obstructed** by a wall or another guard. A cell is **guarded** if there is **at least** one guard that can see it.

Return* the number of unoccupied cells that are not guarded.*

**Example 1:**

Input:m = 4, n = 6, guards = [[0,0],[1,1],[2,3]], walls = [[0,1],[2,2],[1,4]]Output:7Explanation:The guarded and unguarded cells are shown in red and green respectively in the above diagram. There are a total of 7 unguarded cells, so we return 7.

**Example 2:**

Input:m = 3, n = 3, guards = [[1,1]], walls = [[0,1],[1,0],[2,1],[1,2]]Output:4Explanation:The unguarded cells are shown in green in the above diagram. There are a total of 4 unguarded cells, so we return 4.

**Constraints:**

`1 <= m, n <= 10`

^{5}`2 <= m * n <= 10`

^{5}`1 <= guards.length, walls.length <= 5 * 10`

^{4}`2 <= guards.length + walls.length <= m * n`

`guards[i].length == walls[j].length == 2`

`0 <= row`

_{i}, row_{j}< m`0 <= col`

_{i}, col_{j}< n- All the positions in
`guards`

and`walls`

are**unique**.

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