墙与门

class Solution:    def wallsAndGates(self, rooms):        from collections import deque        rows, cols = len(rooms), len(rooms[0])        q = deque((r, c) for r in range(rows) for c in range(cols) if rooms[r][c] == 0)        while q:            r, c = q.popleft()            for dr, dc in ((1,0),(-1,0),(0,1),(0,-1)):                nr, nc = r + dr, c + dc                if 0 <= nr < rows and 0 <= nc < cols and rooms[nr][nc] == 2147483647:                    rooms[nr][nc] = rooms[r][c] + 1                    q.append((nr, nc))

Python

# 多源 BFS 骨架q = deque(所有门的坐标)        # 所有源同时入队，距离 0while q:    r, c = q.popleft()    for 四个方向 nr, nc:        if 在界内 and rooms[nr][nc]==∞:   # 只填未访问的空房间            rooms[nr][nc] = rooms[r][c] + 1            q.append((nr, nc))