add cycle

README.md

@@ -57,6 +57,7 @@ Try to keep the interface and variable name consistent with the original book wh
   * [DepthFirstPaths](algs4/depth_first_paths.py)
   * [BreadthFirstPaths](algs4/breadth_first_paths.py)
   * [CC](algs4/cc.py)
+  * [Cycle](algs4/cycle.py)
 
 * 5 STRING
 

algs4/depth_first_paths.py

@@ -34,20 +34,20 @@
 class DepthFirstPaths:
 
     def __init__(self, G, s):
-        self._marked = [False for _ in range(G.V)]
+        self.marked = [False for _ in range(G.V)]
         self.edge_to = [0 for _ in range(G.V)]
         self.s = s
         self.dfs(G, s)
 
     def dfs(self, G, v):
-        self._marked[v] = True
+        self.marked[v] = True
         for w in G.adj[v]:
-            if not self._marked[w]:
+            if not self.marked[w]:
                 self.edge_to[w] = v
                 self.dfs(G, w)
 
     def has_path_to(self, v):
-        return self._marked[v]
+        return self.marked[v]
 
     def path_to(self, v):
         if not self.has_path_to(v):

algs4/depth_first_search.py

@@ -21,20 +21,17 @@
 class DepthFirstSearch:
 
     def __init__(self, G, s):
-        self._marked = [False for _ in range(G.V)]
+        self.marked = [False for _ in range(G.V)]
         self.count = 0
         self.dfs(G, s)
 
     def dfs(self, G, v):
-        self._marked[v] = True
+        self.marked[v] = True
         self.count += 1
         for w in G.adj[v]:
-            if not self._marked[w]:
+            if not self.marked[w]:
                 self.dfs(G, w)
 
-    def marked(self, s):
-        return self._marked[s]
-
 if __name__ == '__main__':
     import sys
     print(sys.argv)
@@ -48,7 +45,7 @@ def marked(self, s):
         g.add_edge(v, w)
     search = DepthFirstSearch(g, s)
     for v in range(g.V):
-        if search.marked(v):
+        if search.marked[v]:
             print(str(v) + " ")
     if search.count == g.V:
         print("connected")