class Solution {
public:
vector<int> d{1, 0, -1, 0, 1};
vector<vector<int>> pacificAtlantic(vector<vector<int>>& heights) {
int n = heights.size(), m = heights[0].size();
vector<vector<int>> v1(n, vector<int>(m));
vector<vector<int>> v2(n, vector<int>(m));
vector<vector<int>> ans;
for (int i = 0; i < n; i++) {
bfs(heights, v1, i, 0);
bfs(heights, v2, i, m - 1);
}
for (int i = 0; i < m; i++) {
bfs(heights, v1, 0, i);
bfs(heights, v2, n - 1, i);
}
for (int i = 0; i < heights.size(); i++) {
for (int j = 0; j < heights[0].size(); j++) {
if (v1[i][j] && v2[i][j]) ans.push_back({i, j});
}
}
return ans;
}
void bfs(vector<vector<int>>& heights, vector<vector<int>>& vis, int i, int j){
queue<pair<int,int>> q;
int n = heights.size(), m = heights[0].size();
q.push({i, j});
vis[i][j] = true;
while (!q.empty()) {
pair<int, int> t = q.front(); q.pop();
int i = t.first, j = t.second;
for (int k = 0; k < 4; k++) {
int fx = i + d[k];
int fy = j + d[k + 1];
if (fx >= 0 && fy >= 0 && fx < n && fy < m && heights[i][j] <= heights[fx][fy] && !vis[fx][fy]) {
q.push({fx, fy});
vis[fx][fy] = true;
}
}
}
}
};