Merge branch 'master' of github.com:faif/python-patterns

graph_search.py

@@ -0,0 +1,75 @@
+class GraphSearch:
+    """Graph search emulation in python, from source http://www.python.org/doc/essays/graphs/"""
+    
+    def __init__(self, graph):
+        self.graph = graph 
+    
+    def find_path(self, start, end, path=[]):
+        self.start = start
+        self.end = end
+        self.path = path
+        
+        self.path+=[self.start]
+        if self.start == self.end:
+            return self.path
+        if not self.graph.has_key(self.start):
+            return None
+        for node in self.graph[self.start]:
+            if node not in self.path:
+                newpath = self.find_path(node, self.end, self.path)
+                if newpath:
+                    return newpath
+        return None
+    
+    def find_all_path(self, start, end, path=[]):            
+        self.start = start
+        self.end = end
+        self.path = path
+        self.path+=[self.start]
+        if self.start == self.end:
+            return [self.path]
+        if not self.graph.has_key(self.start):
+            return []
+        paths=[]
+        for node in self.graph[self.start]:
+            if node not in self.path:
+                newpaths = self.find_all_path(node, self.end, self.path)
+                for newpath in newpaths:
+                    paths.append(newpath)                
+        return paths
+    
+    def find_shortest_path(self, start, end, path=[]):         
+        self.start = start
+        self.end = end
+        self.path = path
+        
+        self.path+=[self.start]
+        if self.start == self.end:
+            return self.path
+        if not self.graph.has_key(self.start):
+            return None
+        shortest = None
+        for node in self.graph[self.start]:
+            if node not in self.path:
+                newpath = self.find_shortest_path(node, self.end, self.path)
+                if newpath:
+                    if not shortest or len(newpath) < len(shortest):
+                        shortest = newpath
+        return shortest
+
+#example of graph usage
+graph = {'A':['B', 'C'],
+         'B': ['C', 'D'],
+         'C': ['D'],
+         'D': ['C'],
+         'E': ['F'],
+         'F': ['C']   
+            }
+
+#inistialization of new graph search object
+graph1 = GraphSearch(graph)
+
+
+print graph1.find_path('A', 'D')
+print graph1.find_all_path('A', 'D')
+print graph1.find_shortest_path('A', 'D')