### pacificAtlantic 
from collections import deque
from typing import *
def f_gold(heights: List[List[int]]) -> List[List[int]]:
    def bfs(q, vis):
        while q:
            for _ in range(len(q)):
                i, j = q.popleft()
                for a, b in [[0, -1], [0, 1], [1, 0], [-1, 0]]:
                    x, y = i + a, j + b
                    if (
                        0 <= x < m
                        and 0 <= y < n
                        and (x, y) not in vis
                        and heights[x][y] >= heights[i][j]
                    ):
                        vis.add((x, y))
                        q.append((x, y))
    m, n = len(heights), len(heights[0])
    vis1, vis2 = set(), set()
    q1 = deque()
    q2 = deque()
    for i in range(m):
        for j in range(n):
            if i == 0 or j == 0:
                vis1.add((i, j))
                q1.append((i, j))
            if i == m - 1 or j == n - 1:
                vis2.add((i, j))
                q2.append((i, j))
    bfs(q1, vis1)
    bfs(q2, vis2)
    return [
        (i, j)
        for i in range(m)
        for j in range(n)
        if (i, j) in vis1 and (i, j) in vis2
    ]