Create 909-Snakes-and-Ladders.py

Author: neetcode-gh

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