Time: 2593 ms (7.62%), Space: 52.6 MB (18.1%) - LeetHub

Author: hogan-tech

2147-number-of-ways-to-divide-a-long-corridor/2147-number-of-ways-to-divide-a-long-corridor.py

@@ -0,0 +1,30 @@
+# time complexity: O(n)
+# space complexity: O(n)
+class Solution:
+    def numberOfWays(self, corridor: str) -> int:
+        MOD = 1_000_000_007
+        cache = [[-1] * 3 for _ in range(len(corridor))]
+
+        def count(index, seats):
+            if index == len(corridor):
+                return 1 if seats == 2 else 0
+            if cache[index][seats] != -1:
+                return cache[index][seats]
+            if seats == 2:
+                if corridor[index] == "S":
+                    result = count(index + 1, 1)
+                else:
+                    result = (count(index + 1, 0) + count(index + 1, 2)) % MOD
+            else:
+                if corridor[index] == "S":
+                    result = count(index + 1, seats + 1)
+                else:
+                    result = count(index + 1, seats)
+            cache[index][seats] = result
+            return cache[index][seats]
+
+        return count(0, 0)
+
+
+corridor = "PPSPSP"
+print(Solution().numberOfWays(corridor))