def bfs(root):
    queue = deque([root])
    visited = set([root])
    while len(queue) > 0:
        node = queue.popleft()
        for neighbor in get_neighbors(node):
            if neighbor in visited:
                continue
            queue.append(neighbor)
            visited.add(neighbor)

def dfs(root, visited):
    for neighbor in get_neighbors(root):
        if neighbor in visited:
            continue
        visited.add(neighbor)
        dfs(neighbor, visited)

num_rows, num_cols = len(grid), len(grid[0])
def get_neighbors(coord):
    row, col = coord
    delta_row = [-1, 0, 1, 0]
    delta_col = [0, 1, 0, -1]
    res = []
    for i in range(len(delta_row)):
        neighbor_row = row + delta_row[i]
        neighbor_col = col + delta_col[i]
        if 0 <= neighbor_row < num_rows and 0 <= neighbor_col < num_cols:
            res.append((neighbor_row, neighbor_col))
    return res

from collections import deque

def bfs(starting_node):
    queue = deque([starting_node])
    visited = set([starting_node])
    while len(queue) > 0:
        node = queue.popleft()
        for neighbor in get_neighbors(node):
            if neighbor in visited:
                continue
            # Do stuff with the node if required
            # ...
            queue.append(neighbor)
            visited.add(neighbor)