leetcode

0 class Solution {

1 public:

2 int countUnguarded(const int n, const int m, const vector<vector<int>> &guards,

3 const vector<vector<int>> &walls) const {

4 const auto idx = [m](int x, int y) { return x * m + y; };

5

6 bitset<100001> stop = 0, seen = 0;

7 for (const auto &wall : walls)

8 stop.set(idx(wall[0], wall[1]));

9 for (const auto &guard : guards)

10 stop.set(idx(guard[0], guard[1]));

11

12 static const int offset[] = {-1, 0, 1, 0, -1};

13

14 int res = m * n - size(walls) - size(guards);

15 for (const auto &guard : guards) {

16 for (int k = 0; k < 4; k++) {

17 int x = guard[0] + offset[k], y = guard[1] + offset[k + 1];

18 while (x >= 0 && x < n && y >= 0 && y < m) {

19 const int index = idx(x, y);

20 if (stop.test(index)) break;

21 if (!seen.test(index)) res--;

22 seen.set(index);

23 x += offset[k], y += offset[k + 1];

24 }

25 }

26 }

27

28 return res;

29 }

30 };