#273 Pacific Atlantic Water Flow

Given a rectangular island represented by a matrix heights where heights[r][c] represents the height above sea level at position (r,c).

The island is surrounded by:

• Pacific Ocean: top and left edges
• Atlantic Ocean: bottom and right edges

Water flow rules:

• Can flow in four directions (up, down, left, right)
• Can only flow to cells of equal or lower height
• Can flow into oceans from adjacent cells

Return all cells where water can flow to both oceans, represented as [row, col] coordinates.

Constraints:

• 1 ≤ matrix dimensions ≤ 100
• 0 ≤ height values ≤ 1000

Examples:

// Example 1:
const heights1 = [
  [4, 2, 7, 3, 4],
  [7, 4, 6, 4, 7],
  [6, 3, 5, 3, 6],
];
console.log(pacificAtlantic(heights1));
// Output: [[0,2],[0,4],[1,0],[1,1],[1,2],[1,3],[1,4],[2,0]]
// Explanation: These cells can flow to both oceans

// Example 2:
const heights2 = [[1], [1]];
console.log(pacificAtlantic(heights2));
// Output: [[0,0],[1,0]]
// Explanation: Both cells can flow to both oceans