<p>There is an <code>m x n</code> rectangular island that borders both the <strong>Pacific Ocean</strong> and <strong>Atlantic Ocean</strong>. The <strong>Pacific Ocean</strong> touches the island&#39;s left and top edges, and the <strong>Atlantic Ocean</strong> touches the island&#39;s right and bottom edges.</p>

<p>The island is partitioned into a grid of square cells. You are given an <code>m x n</code> integer matrix <code>heights</code> where <code>heights[r][c]</code> represents the <strong>height above sea level</strong> of the cell at coordinate <code>(r, c)</code>.</p>

<p>The island receives a lot of rain, and the rain water can flow to neighboring cells directly north, south, east, and west if the neighboring cell&#39;s height is <strong>less than or equal to</strong> the current cell&#39;s height. Water can flow from any cell adjacent to an ocean into the ocean.</p>

<p>Return <em>a <strong>2D list</strong> of grid coordinates </em><code>result</code><em> where </em><code>result[i] = [r<sub>i</sub>, c<sub>i</sub>]</code><em> denotes that rain water can flow from cell </em><code>(r<sub>i</sub>, c<sub>i</sub>)</code><em> to <strong>both</strong> the Pacific and Atlantic oceans</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2021/06/08/waterflow-grid.jpg" style="width: 400px; height: 400px;" />
<pre>
<strong>Input:</strong> heights = [[1,2,2,3,5],[3,2,3,4,4],[2,4,5,3,1],[6,7,1,4,5],[5,1,1,2,4]]
<strong>Output:</strong> [[0,4],[1,3],[1,4],[2,2],[3,0],[3,1],[4,0]]
<strong>Explanation:</strong> The following cells can flow to the Pacific and Atlantic oceans, as shown below:
[0,4]: [0,4] -&gt; Pacific Ocean 
&nbsp;      [0,4] -&gt; Atlantic Ocean
[1,3]: [1,3] -&gt; [0,3] -&gt; Pacific Ocean 
&nbsp;      [1,3] -&gt; [1,4] -&gt; Atlantic Ocean
[1,4]: [1,4] -&gt; [1,3] -&gt; [0,3] -&gt; Pacific Ocean 
&nbsp;      [1,4] -&gt; Atlantic Ocean
[2,2]: [2,2] -&gt; [1,2] -&gt; [0,2] -&gt; Pacific Ocean 
&nbsp;      [2,2] -&gt; [2,3] -&gt; [2,4] -&gt; Atlantic Ocean
[3,0]: [3,0] -&gt; Pacific Ocean 
&nbsp;      [3,0] -&gt; [4,0] -&gt; Atlantic Ocean
[3,1]: [3,1] -&gt; [3,0] -&gt; Pacific Ocean 
&nbsp;      [3,1] -&gt; [4,1] -&gt; Atlantic Ocean
[4,0]: [4,0] -&gt; Pacific Ocean 
       [4,0] -&gt; Atlantic Ocean
Note that there are other possible paths for these cells to flow to the Pacific and Atlantic oceans.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> heights = [[1]]
<strong>Output:</strong> [[0,0]]
<strong>Explanation:</strong> The water can flow from the only cell to the Pacific and Atlantic oceans.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>m == heights.length</code></li>
	<li><code>n == heights[r].length</code></li>
	<li><code>1 &lt;= m, n &lt;= 200</code></li>
	<li><code>0 &lt;= heights[r][c] &lt;= 10<sup>5</sup></code></li>
</ul>

class Solution {
public:
void pcfHelper(std::vector<std::vector<int>>& heights, std::set<std::vector<int>>& ans, bool pacific) {
    std::set<std::vector<int>> visited;
    std::queue<std::vector<int>> q;
    if (pacific) {
        for (int j = 0; j < heights[0].size(); j++) {
            q.push({0, j});
        }
        for (int i = 0; i < heights.size(); i++) {
            q.push({i, 0});
        }
    } else {
        for (int j = 0; j < heights[0].size(); j++) {
            int ins = heights.size()-1;
            q.push({ins,j});
        }
        for (int i = 0; i < heights.size(); i++) {
            int ins = heights[0].size()-1;
            q.push({i, ins});
        }
    }

    while (q.size()) {
        auto cur = q.front();
        q.pop();
        ans.insert(cur);
        int i = cur[0];
        int j = cur[1];
        for (int ii = -1; ii < 2; ii++) {
            if (ii == 0) {
                continue;
            }
            if (i + ii >= 0 && i + ii < heights.size() && heights[i][j] <= heights[i+ii][j]) {
                if (visited.count({i+ii,j})) {
                    continue;
                }
                visited.insert({i+ii,j});
                q.push({i + ii, j});
            }
        }

        for (int jj = -1; jj < 2; jj++) {
            if (jj == 0) {
                continue;
            }
            int i = cur[0];
            int j = cur[1];
            if (j + jj >= 0 && j + jj < heights[0].size() && heights[i][j] <= heights[i][j+jj]) {
                if (visited.count({i,j+jj})) {
                    continue;
                }
                visited.insert({i, j + jj});
                q.push({i, j + jj});
            }
        }
    }


}
    vector<vector<int>> pacificAtlantic(vector<vector<int>>& heights) {

    std::vector<std::vector<int>> ans;
    std::set<std::vector<int>> pacificFlowers;
    std::set<std::vector<int>> atlanticFlowers;
    pcfHelper(heights, pacificFlowers, true);
    pcfHelper(heights, atlanticFlowers, false);

    for (auto p: pacificFlowers) {
        if (atlanticFlowers.count(p)) {
            ans.push_back(p);
        }
    }
    return ans;
    }
};
42000