Update pyramid-transition-matrix.py

Python/pyramid-transition-matrix.py

@@ -49,7 +49,7 @@ def pyramidTransition(self, bottom, allowed):
         def pyramidTransitionHelper(bottom, edges, lookup):
             def dfs(bottom, edges, new_bottom, idx, lookup):
                 if idx == len(bottom)-1:
-                    return pyramidTransitionHelper(new_bottom, edges, lookup)
+                    return pyramidTransitionHelper("".join(new_bottom), edges, lookup)
                 for i in edges[ord(bottom[idx])-ord('A')][ord(bottom[idx+1])-ord('A')]:
                     new_bottom[idx] = chr(i+ord('A'));
                     if dfs(bottom, edges, new_bottom, idx+1, lookup):
@@ -58,9 +58,9 @@ def dfs(bottom, edges, new_bottom, idx, lookup):
 
             if len(bottom) == 1:
                 return True
-            if "".join(bottom) in lookup:
+            if bottom in lookup:
                 return False
-            lookup.add("".join(bottom))
+            lookup.add(bottom)
             for i in xrange(len(bottom)-1):
                 if not edges[ord(bottom[i])-ord('A')][ord(bottom[i+1])-ord('A')]:
                     return False
@@ -71,4 +71,3 @@ def dfs(bottom, edges, new_bottom, idx, lookup):
         for s in allowed:
             edges[ord(s[0])-ord('A')][ord(s[1])-ord('A')].append(ord(s[2])-ord('A'))
         return pyramidTransitionHelper(bottom, edges, set())
-