vector<pair<int, int>> pacificAtlantic(vector<vector<int>>& matrix) {
vector<pair<int,int>> res;
if(!matrix.size() || !matrix[0].size()) return res;
int m = matrix.size(), n = matrix[0].size();
queue<pair<int,int>> qA, qP;
vector<vector<bool>> pacific(m,vector<bool>(n, false));
vector<vector<bool>> atlantic(m,vector<bool>(n, false));
vector<pair<int,int>> dir{{1,0},{-1,0},{0,1},{0,-1}};
for(int i = 0; i < m; ++i){
qP.push({i,0});
qA.push({i,n-1});
pacific[i][0] = true;
atlantic[i][n-1] = true;
}
for(int i = 0; i < n; ++i){
qP.push({0,i});
qA.push({m-1,i});
pacific[0][i] = true;
atlantic[m-1][i] = true;
}
while(!qP.empty()){
pair<int,int> cur = qP.front();
qP.pop();
for(auto d : dir){
int x = cur.first+d.first, y = cur.second+d.second;
if(x>=0&&y>=0&&x<m&&y<n&&!pacific[x][y]&&matrix[x][y] >= matrix[cur.first][cur.second]){
pacific[x][y] = true;
qP.push({x,y});
}
}
}
while(!qA.empty()){
pair<int,int> cur = qA.front();
qA.pop();
for(auto d : dir){
int x = cur.first+d.first, y = cur.second+d.second;
if(x>=0&&y>=0&&x<m&&y<n&&!atlantic[x][y]&&matrix[x][y] >= matrix[cur.first][cur.second]){
atlantic[x][y] = true;
qA.push({x,y});
}
}
}
for(int i = 0; i < m; ++i){
for(int j = 0; j < n; ++j){
if(pacific[i][j] && atlantic[i][j])
res.push_back({i,j});
}
}
return res;
}
vector<pair<int, int>> pacificAtlantic(vector<vector<int>>& matrix) {
if (matrix.empty() || matrix[0].empty()) return {};
vector<pair<int, int>> res;
int m = matrix.size(), n = matrix[0].size();
vector<vector<bool>> pacific(m, vector<bool>(n, false));
vector<vector<bool>> atlantic(m, vector<bool>(n, false));
for (int i = 0; i < m; ++i) {
dfs(matrix, pacific, INT_MIN, i, 0);
dfs(matrix, atlantic, INT_MIN, i, n - 1);
}
for (int i = 0; i < n; ++i) {
dfs(matrix, pacific, INT_MIN, 0, i);
dfs(matrix, atlantic, INT_MIN, m - 1, i);
}
for (int i = 0; i < m; ++i) {
for (int j = 0; j < n; ++j) {
if (pacific[i][j] && atlantic[i][j]) {
res.push_back({i, j});
}
}
}
return res;
}
