leetcode

0 class Solution {

1 int n, m;

2 bool valid(int x, int y) { return x >= 0 && x < n && y >= 0 && y < m; }

3

4 void flood_fill(vector<vector<int>> &grid, int x, int y) {

5 grid[x][y] = 1;

6 if (valid(x + 1, y) && !grid[x + 1][y]) flood_fill(grid, x + 1, y);

7 if (valid(x - 1, y) && !grid[x - 1][y]) flood_fill(grid, x - 1, y);

8 if (valid(x, y + 1) && !grid[x][y + 1]) flood_fill(grid, x, y + 1);

9 if (valid(x, y - 1) && !grid[x][y - 1]) flood_fill(grid, x, y - 1);

10 }

11

12 public:

13 int closedIsland(vector<vector<int>> &grid) {

14 n = grid.size(), m = grid[0].size();

15 for (int i = 0; i < n; i++) {

16 if (!grid[i][0]) flood_fill(grid, i, 0);

17 if (!grid[i][m - 1]) flood_fill(grid, i, m - 1);

18 }

19 for (int i = 0; i < m; i++) {

20 if (!grid[0][i]) flood_fill(grid, 0, i);

21 if (!grid[n - 1][i]) flood_fill(grid, n - 1, i);

22 }

23

24 int res = 0;

25 for (int i = 1; i < n - 1; i++) {

26 for (int j = 1; j < m - 1; j++) {

27 if (grid[i][j]) continue;

28 flood_fill(grid, i, j);

29 res++;

30 }

31 }

32

33 return res;

34 }

35 };