added loop detection

contracts_test.txt

@@ -0,0 +1,8 @@
+1 Chennai Bangalore 100
+1 Bangalore Chennai 100
+2 Bangalore Kolkata 200
+2 Bangalore Mumbai 300
+2 Bangalore Cochin 400
+3 Cochin Kolkata 200
+3 Mumbai Chennai 300
+3 Chennai Cochin 500

cyclic_contracts.py

@@ -1,8 +1,10 @@
+
 class Route(object):
     """docstring for Route."""
-    def __init__(self, route_id, load,src,dst):
+    def __init__(self, route_id, contract_id, load,src,dst):
         super(Route, self).__init__()
         self.route_id = route_id
+        self.contract_id = contract_id
         self.load = load
         self.src = src
         self.dst = dst
@@ -27,6 +29,10 @@ class Transporter(object):
         super(Transporter, self).__init__()
         self.contracts = contracts
 
+    @classmethod
+    def from_file(cls,c_file):
+        return cls(cls.read_contracts(c_file))
+
     @staticmethod
     def read_contracts(c_file):
         c_lines = open(c_file,'r').readlines()
@@ -35,15 +41,48 @@ class Transporter(object):
             (c_id,src,dst,load) = l.split(' ')
             if c_dict.has_key(c_id):
                 route_id = len(c_dict[c_id])
-                c_dict[c_id].append(Route(route_id,load,src,dst))
+                c_dict[c_id].append(Route(route_id,int(c_id),load,src,dst))
             else:
-                c_dict[c_id] = [Route(0,load,src,dst)]
+                c_dict[c_id] = [Route(0,int(c_id),load,src,dst)]
-
         contrants = []
         for c_id in c_dict:
             contrants.append(Contract(int(c_id),c_dict[c_id]))
-
         return contrants
 
+    def routes(self):
+        all_routes = []
+        routes_map = {}
+        for c in self.contracts:
+            for r in c.routes:
+                all_routes.append(r)
+                if routes_map.has_key(r.src):
+                    routes_map[r.src].append(r.dst)
+                else:
+                    routes_map[r.src]= [r.dst]
+        return all_routes,routes_map
 
-print Transporter.read_contracts('./contracts.txt')
+    def is_cyclic(self):
+        return circular_dep(self.routes()[1])
+
+def find_loop(elem,dep_elem,deps,checked=set()):
+    if dep_elem in checked or not deps.has_key(dep_elem):
+        return (False,len(checked))
+    else:
+        checked.add(dep_elem)
+    for c in deps[dep_elem]:
+        if elem == c:
+            return (True,len(checked))
+    for c in deps[dep_elem]:
+        c_loop = find_loop(elem,c,deps,checked)
+        if c_loop[0]:
+            return c_loop
+    return (False,len(checked))
+    
+def circular_dep(deps):
+    dep_state = []
+    for k in deps.keys():
+        circ_dep_k = find_loop(k,k,deps,set())
+        dep_state.append((k,circ_dep_k))
+    return dep_state
+
+print Transporter.from_file('./contracts_test.txt').is_cyclic()