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 thegrid
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 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.
Example 4:
Input: grid = [["#","#","#","#","#","#","#"], ["#","S","#",".","B","T","#"], ["#","#","#","#","#","#","#"]] Output: -1
Constraints:
m == grid.length
n == grid[i].length
1 <= m <= 20
1 <= n <= 20
grid
contains only characters'.'
,'#'
,'S'
,'T'
, or'B'
.- There is only one character
'S'
,'B'
and'T'
in thegrid
.