human
Solve in Python:
Storekeeper is a game in which the player pushes boxes around in a warehouse trying to get them to target locations.
The game is represented by a grid of size m x n, where each element is a wall, floor, or a box.
Your task is move the box 'B' to the target position 'T' under the following rules:

Player is represented by character 'S' and can move up, down, left, right in the grid if it is a floor (empy cell).
Floor is represented by character '.' that means free cell to walk.
Wall is represented by character '#' that means obstacle  (impossible to walk there). 
There is only one box 'B' and one target cell 'T' in the grid.
The box can be moved to an adjacent free cell by standing next to the box and then moving in the direction of the box. This is a push.
The player cannot walk through the box.

Return the minimum number of pushes to move the box to the target. If there is no way to reach the target, return -1.
 
Example 1:

Input: grid = [["#","#","#","#","#","#"],
               ["#","T","#","#","#","#"],
               ["#",".",".","B",".","#"],
               ["#",".","#","#",".","#"],
               ["#",".",".",".","S","#"],
               ["#","#","#","#","#","#"]]
Output: 3
Explanation: We return only the number of times the box is pushed.
Example 2:
Input: grid = [["#","#","#","#","#","#"],
               ["#","T","#","#","#","#"],
               ["#",".",".","B",".","#"],
               ["#","#","#","#",".","#"],
               ["#",".",".",".","S","#"],
               ["#","#","#","#","#","#"]]
Output: -1

Example 3:
Input: grid = [["#","#","#","#","#","#"],
               ["#","T",".",".","#","#"],
               ["#",".","#","B",".","#"],
               ["#",".",".",".",".","#"],
               ["#",".",".",".","S","#"],
               ["#","#","#","#","#","#"]]
Output: 5
Explanation:  push the box down, left, left, up and up.

Example 4:
Input: grid = [["#","#","#","#","#","#","#"],
               ["#","S","#",".","B","T","#"],
               ["#","#","#","#","#","#","#"]]
Output:...
assistant
#Here is the Python code you requested.

class Solution:
    def minPushBox(self, grid: List[List[str]]) -> int:
        m, n = len(grid), len(grid[0])
        moves = [(0, 1), (0, -1), (1, 0), (-1, 0)]
        
        
        def check(p1, p2, t1, t2, b1, b2):#g is new grid
            visited = visited = [[False for _ in range(n)] for _ in range(m)]
            queue = collections.deque()
            queue.append((p1, p2))
            visited[p1][p2] = True
            
            while queue:
                x, y = queue.popleft()
                if (x, y) == (t1, t2):
                    return True
                for dx, dy in moves:
                    nx, ny = x + dx, y + dy
                    if 0 <= nx < m  and 0 <= ny < n:
                        if visited[nx][ny]: continue
                        if (nx, ny) == (t1, t2): return True
                        if (nx, ny) != (b1, b2) and grid[nx][ny] != '#':
                            queue.append((nx, ny))
                            visited[nx][ny] = True
            return False
        
        def inbound(x, y):
            return 0 <= x < m and 0 <= y < n
        
        for i in range(m):
            for j in range(n):
                if grid[i][j] != '#':
                    if grid[i][j] == 'S':
                        player = (i, j)
                    elif grid[i][j] == 'B':
                        box = (i, j)
                    elif grid[i][j] == 'T':
                        end = (i, j)
        #player box end
        p1, p2 = player
        b1, b2 = box
        e1, e1 = end    
        
        visited = set()
        step = -1
        
        queue = collections.deque()
        queue.append((b1, b2, p1, p2))
        
        while queue:
            step += 1
            for _ in range(len(queue)):#别忘了是层序遍历！！！
                x, y, p1, p2 = queue.popleft()
                #up
                if inbound(x - 1, y) and inbound(x + 1, y) and grid[x + 1][y] != '#' and check(p1, p2, x + 1, y, x, y):
                    if (x - 1, y, x, y) not in visited:
                 ...