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] = [rowi, coli] and walls[j] = [rowj, colj] represent the positions of the ith guard and jth wall respectively.
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.
\n\nReturn the number of unoccupied cells that are not guarded.
\n\n\n
Example 1:
\n![\"\"](\"https://assets.leetcode.com/uploads/2022/03/10/example1drawio2.png\")
\n\nInput: m = 4, n = 6, guards = [[0,0],[1,1],[2,3]], walls = [[0,1],[2,2],[1,4]]\nOutput: 7\nExplanation: The guarded and unguarded cells are shown in red and green respectively in the above diagram.\nThere are a total of 7 unguarded cells, so we return 7.\n\n\n
Example 2:
\n![\"\"](\"https://assets.leetcode.com/uploads/2022/03/10/example2drawio.png\")
\n\nInput: m = 3, n = 3, guards = [[1,1]], walls = [[0,1],[1,0],[2,1],[1,2]]\nOutput: 4\nExplanation: The unguarded cells are shown in green in the above diagram.\nThere are a total of 4 unguarded cells, so we return 4.\n\n\n
\n
Constraints:
\n\n1 <= m, n <= 1052 <= m * n <= 1051 <= guards.length, walls.length <= 5 * 1042 <= guards.length + walls.length <= m * nguards[i].length == walls[j].length == 20 <= rowi, rowj < m0 <= coli, colj < nguards and walls are unique.Compiled with clang 11 using the latest C++ 20 standard.
Your code is compiled with level two optimization (-O2). AddressSanitizer is also enabled to help detect out-of-bounds and use-after-free bugs.
Most standard library headers are already included automatically for your convenience.
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