Walls and Gates – Python 3 (Week 12 – 11)

    class Solution:
    """
    @param rooms: m x n 2D grid
    @return: nothing
    """
    def wallsAndGates(self, rooms):
        # write your code here
        
        if not rooms or len(rooms) == 0 or len(rooms[0]) == 0:
            return
        
        m, n = len(rooms[0]), len(rooms)
        import queue
        qx = queue.Queue()
        qy = queue.Queue()
        
        dx = [0, 0, 1, -1]
        dy = [1, -1, 0, 0]
        
        for i in range(n):
            for j in range(m):
                if rooms[i][j] == 0:
                    qx.put(i)
                    qy.put(j)
        
        
        while not qx.empty():
            cx = qx.get()
            cy = qy.get()
            
            for i in range(4):
                nx = cx +dx[i]
                ny = cy +dy[i]
                if nx >= 0 and nx < n and ny >= 0 and ny < m and rooms[nx][ny] == 2**31 - 1:
                    qx.put(nx)
                    qy.put(ny)
                    rooms[nx][ny] = rooms[cx][cy] + 1