Create grader.py

library2/grader.py

@@ -0,0 +1,112 @@
+N = input()
+dictionary = {}
+word_idx = {}
+for i in range(N):
+    line = raw_input()
+    sp = line.split(": ")
+    word = sp[0]
+    defn = sp[1].split(" ")
+    dictionary[word] = defn
+    word_idx[word] = i
+#print dictionary
+
+graph = {} #adj-list graph of word dependencies
+for i in range(N):
+    graph[i] = []
+for word in dictionary:
+    idx = word_idx[word]
+    for dword in dictionary[word]:
+        toidx = word_idx[dword]
+        graph[idx].append(toidx)
+
+#print graph
+
+
+index = 0
+
+components = []
+S = []
+v_index = {}
+v_lowlink = {}
+v_onStack = {}
+def strongConnect(v):
+    global index
+    global components
+    global S
+    global v_index
+    global v_lowlink
+    global v_onStack
+
+    v_index[v] = index
+    v_lowlink[v] = index
+    index += 1
+    S.append(v)
+    v_onStack[v] = True
+
+    # for edges of V
+    for w in graph[v]:
+        if w not in v_index:
+            strongConnect(w)
+            v_lowlink[v] = min(v_lowlink[v], v_lowlink[w])
+        elif v_onStack[w]:
+            v_lowlink[v] = min(v_lowlink[v], v_lowlink[w])
+
+    if v_lowlink[v] == v_index[v]:
+        component = []
+        while True:
+            w = S.pop()
+            v_onStack[w] = False
+            component.append(w)
+            if w==v:
+                break
+        components.append(component)
+def SCC(graph):
+    global index
+    global components
+    global S
+    global v_index
+    global v_lowlink
+    global v_onStack
+
+    index = 0
+    components = []
+    S = []
+    v_index = {}
+    v_lowlink = {}
+    v_onStack = {}
+    for v in graph:
+        if v not in v_index:
+            strongConnect(v)
+    return components
+
+
+comps = SCC(graph)
+#print comps
+newnodemap = {}
+for idx in range(len(comps)):
+    comp = comps[idx]
+    for node in comp:
+        newnodemap[node] = idx
+
+newgraph = {}
+
+for idx in range(len(comps)):
+    comp = comps[idx]
+    outgoing = set([])
+    for node in comp:
+        nodeout = graph[node]
+        newnodeout = set([])
+        for no in nodeout:
+            newnodeout.add(newnodemap[no])
+        outgoing = outgoing.union(newnodeout)
+    outgoing.discard(idx)
+    newgraph[idx] = list(outgoing)
+#print newgraph
+# count number of nodes with no incoming edges
+
+ans = 0
+for node in newgraph:
+    if len(newgraph[node])==0:
+        ans += 1
+
+print ans