A 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 an m x n
grid of characters grid
where each element is a wall, floor, or box.
Your task is to move the box 'B'
to the target position 'T'
under the following rules:
 The character
'S'
represents the player. The player can move up, down, left, right ingrid
if it is a floor (empty cell).  The character
'.'
represents the floor which means a free cell to walk.  The character
'#'
represents the wall which means an obstacle (impossible to walk there).  There is only one box
'B'
and one target cell'T'
in thegrid
.  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.
Constraints:
m == grid.length
n == grid[i].length
1 <= m, n <= 20
grid
contains only characters'.'
,'#'
,'S'
,'T'
, or'B'
. There is only one character
'S'
,'B'
, and'T'
in thegrid
.

