leetcode

0 // Matrix BFS/Flood fill

1

2 typedef vector<vector<int>> Matrix;

3 typedef queue<pair<int, int>> Queue;

4 const vector<pair<int, int>> offsets = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};

5

6 int n, m;

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

8

9 void dfs(Matrix &mat, int x, int y) {

10 Queue q;

11

12 q.push({x, y}), mat[x][y] = 2;

13 while (!q.empty()) {

14 auto [a, b] = q.front();

15 q.pop();

16 for (auto [oa, ob] : offsets) {

17 int x = a + oa, y = b + ob;

18 if (!valid(x, y) || mat[x][y] == 0 || mat[x][y] != 1) continue;

19 mat[x][y] = 2;

20 q.push({x, y});

21 }

22 }

23 }