Create number-of-ways-to-divide-a-long-corridor.py

Author: kamyu104

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

@@ -0,0 +1,20 @@
+# Time:  O(n)
+# Space: O(1)
+
+# greedy, combinatorics
+class Solution(object):
+    def numberOfWays(self, corridor):
+        """
+        :type corridor: str
+        :rtype: int
+        """
+        MOD = 10**9+7
+        result, cnt, j = 1, 0, -1
+        for i, x in enumerate(corridor):
+            if x != 'S':
+                continue
+            cnt += 1
+            if cnt >= 3 and cnt%2:
+                result = result*(i-j)%MOD
+            j = i
+        return result if cnt and cnt%2 == 0 else 0