Time: 25 ms (43.73%) | Memory: 18.2 MB (15.77%) - LeetSync

Author: ata-turhan

945-snakes-and-ladders/snakes-and-ladders.py

@@ -0,0 +1,44 @@
+from typing import List
+from collections import deque
+
+class Solution:
+    def snakesAndLadders(self, board: List[List[int]]) -> int:
+        n: int = len(board)
+        
+        # Helper to map a square label s (1-based) to (row, col) in Boustrophedon layout
+        def get_coordinates(s: int) -> tuple[int, int]:
+            quot, rem = divmod(s - 1, n)
+            row = n - 1 - quot
+            if quot % 2 == 0:
+                col = rem
+            else:
+                col = n - 1 - rem
+            return row, col
+        
+        # BFS queue will store (current_square, moves_taken)
+        queue: deque[tuple[int, int]] = deque()
+        queue.append((1, 0))
+        
+        visited: set[int] = set([1])
+        target: int = n * n
+        
+        while queue:
+            square, moves = queue.popleft()
+            
+            # Try all possible dice rolls from 1 to 6
+            for nxt in range(square + 1, min(square + 6, target) + 1):
+                r, c = get_coordinates(nxt)
+                
+                # If there's a snake/ladder at board[r][c], we must take it
+                dest: int = board[r][c] if board[r][c] != -1 else nxt
+                
+                # If we reached the final square, return moves + 1 immediately
+                if dest == target:
+                    return moves + 1
+                
+                if dest not in visited:
+                    visited.add(dest)
+                    queue.append((dest, moves + 1))
+        
+        # If BFS completes without reaching n^2, it's unreachable
+        return -1