73. Pacific Atlantic Water Flow

Medium · Graph

You are given an m×n grid representing the heights of land cells. The Pacific Ocean borders the top and left edges, while the Atlantic Ocean borders the bottom and right edges. Water flows from a cell to any adjacent cell (up, down, left, right) that has an equal or lower height. Find all cells from which water can flow to **both** oceans, and return them as a list of [row, col] coordinates sorted in ascending order.

Examples

Example 1
Input: [[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]]
Output: [[0,4],[1,3],[1,4],[2,2],[3,0],[3,1],[4,0]]
Explanation: Seven cells can flow to both oceans
Example 2
Input: [[1]]
Output: [[0,0]]
Explanation: Single cell touches both

Constraints