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

Author: kamyu104

C++/number-of-ways-to-divide-a-long-corridor.cpp

@@ -0,0 +1,22 @@
+// Time:  O(n)
+// Space: O(1)
+
+// greedy, combinatorics
+class Solution {
+public:
+    int numberOfWays(string corridor) {
+        static const int MOD = 1e9 + 7;
+        int64_t result = 1;
+        int cnt = 0;
+        for (int i = 0, j = -1; i < size(corridor); ++i) {
+            if (corridor[i] != 'S') {
+                continue;
+            }
+            if (++cnt >= 3 && cnt % 2) {
+                result = (result * (i - j)) % MOD;
+            }
+            j = i;
+        }
+        return cnt && cnt % 2 == 0 ? result : 0;
+    }
+};