<h2><a href="https://leetcode.com/problems/pacific-atlantic-water-flow">Pacific Atlantic Water Flow</a></h2> <img src='https://img.shields.io/badge/Difficulty-Medium-orange' alt='Difficulty: Medium' /><hr><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_i, c_i]</code><em> denotes that rain water can flow from cell </em><code>(r_i, c_i)</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;= 10⁵</code></li>

</ul>