Added Graphs

Author: OmkarPathak

pygorithm/data_structures/graph.py

@@ -0,0 +1,60 @@
+# Author: OMKAR PATHAK
+# Created On: 12th August 2017
+
+class AdjacencyList(object):
+    def __init__(self):
+        self.graph = {}
+        self.count = 0
+
+    def print_graph(self):
+        for i  in self.graph:
+            print(i,'->',' -> '.join([str(j) for j in self.graph[i]]))
+
+    def add_edge(self, from_vertex, to_vertex):
+        ''' function to add an edge in the graph '''
+        # check if vertex is already present
+        if from_vertex in self.graph.keys():
+            self.graph[from_vertex].append(to_vertex)
+            self.count += 1
+        else:
+            self.graph[from_vertex] = [to_vertex]
+            self.graph[to_vertex] = []
+            self.count += 1
+
+    def get_code(self):
+        ''' returns the code for the current class '''
+        import inspect
+        return inspect.getsource(AdjacencyList)
+
+class TopologicalSort(AdjacencyList):
+    def topological_sort(self):
+        visited = [False] * self.count           # Marking all vertices as not visited
+        stack = []                               # Stack for storing the vertex
+        for vertex in range(self.count):
+            # Call the recursive function only if not visited
+            if visited[vertex] == False:
+                self.topological_sort_rec(vertex, visited, stack)
+
+        return stack
+
+    # Recursive function for topological Sort
+    def topological_sort_rec(self, vertex, visited, stack):
+
+        # Mark the current node in visited
+        visited[vertex] = True
+
+        # mark all adjacent nodes of the current node
+        try:
+            for adjacent_node in self.graph[vertex]:
+                if visited[adjacent_node] == False:
+                    self.topological_sort_rec(adjacent_node, visited, stack)
+        except KeyError:
+            return
+
+        # Push current vertex to stack which stores the result
+        stack.insert(0,vertex)
+
+    def get_code(self):
+        ''' returns the code for the current class '''
+        import inspect
+        return inspect.getsource(TopologicalSort)