Create 909-Snakes-and-Ladders.py

909-Snakes-and-Ladders.py

@@ -0,0 +1,27 @@
+class Solution:
+ def snakesAndLadders(self, board: List[List[int]]) -> int:
+ length = len(board)
+ board.reverse()
+ def intToPos(square):
+ r = (square - 1) // length
+ c = (square - 1) % length
+ if r % 2:
+ c = length - 1 - c
+ return [r, c]
+
+ q = deque() 
+ q.append([1, 0]) # [square, moves]
+ visit = set()
+ while q:
+ square, moves = q.popleft()
+ for i in range(1, 7):
+ nextSquare = square + i
+ r, c = intToPos(nextSquare)
+ if board[r][c] != -1:
+ nextSquare = board[r][c]
+ if nextSquare == length * length:
+ return moves + 1
+ if nextSquare not in visit:
+ visit.add(nextSquare)
+ q.append([nextSquare, moves + 1])
+ return -1