Merge pull request faif#350 from LCVcode/master

Implemented breadth first search for shortest graph path in graph_search.py

Author: faif

patterns/other/graph_search.py

@@ -1,12 +1,15 @@
 class GraphSearch:
 
     """Graph search emulation in python, from source
-    http://www.python.org/doc/essays/graphs/"""
+    http://www.python.org/doc/essays/graphs/
+
+    dfs stands for Depth First Search
+    bfs stands for Breadth First Search"""
 
     def __init__(self, graph):
         self.graph = graph
 
-    def find_path(self, start, end, path=None):
+    def find_path_dfs(self, start, end, path=None):
         path = path or []
 
         path.append(start)
@@ -18,7 +21,7 @@ def find_path(self, start, end, path=None):
                 if newpath:
                     return newpath
 
-    def find_all_path(self, start, end, path=None):
+    def find_all_paths_dfs(self, start, end, path=None):
         path = path or []
         path.append(start)
         if start == end:
@@ -30,7 +33,7 @@ def find_all_path(self, start, end, path=None):
                 paths.extend(newpaths)
         return paths
 
-    def find_shortest_path(self, start, end, path=None):
+    def find_shortest_path_dfs(self, start, end, path=None):
         path = path or []
         path.append(start)
 
@@ -45,6 +48,29 @@ def find_shortest_path(self, start, end, path=None):
                         shortest = newpath
         return shortest
 
+    def find_shortest_path_bfs(self, start, end):
+        queue = [start]
+        dist_to = {start: 0}
+        edge_to = {}
+
+        while len(queue):
+            value = queue.pop(0)
+            for node in self.graph[value]:
+                if node not in dist_to.keys():
+                    edge_to[node] = value
+                    dist_to[node] = dist_to[value] + 1
+                    queue.append(node)
+            if end in edge_to.values():
+                break
+
+        path = []
+        node = end
+        while dist_to[node] != 0:
+            path.insert(0, node)
+            node = edge_to[node]
+        path.insert(0, start)
+        return path
+
 
 def main():
     """
@@ -54,12 +80,14 @@ def main():
     # initialization of new graph search object
     >>> graph1 = GraphSearch(graph)
 
-    >>> print(graph1.find_path('A', 'D'))
+    >>> print(graph1.find_path_dfs('A', 'D'))
     ['A', 'B', 'C', 'D']
-    >>> print(graph1.find_all_path('A', 'D'))
+    >>> print(graph1.find_all_paths_dfs('A', 'D'))
     [['A', 'B', 'C', 'D'], ['A', 'B', 'D'], ['A', 'C', 'D']]
-    >>> print(graph1.find_shortest_path('A', 'D'))
+    >>> print(graph1.find_shortest_path_dfs('A', 'D'))
     ['A', 'B', 'D']
+    >>> print(graph1.find_shortest_path_bfs('A', 'D'))
+    ['A', 'B', 'C']
     """