(4.1) Route Between Nodes py

CrackingTheCodingInterview/ch04-TreesAndGraphs/routeBetweenNodes.py

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+# Given a directed graph, design an algorithm to find out
+# whether there is a route between two nodes
+
+
+class Node:
+    def __init__(self, value):
+        self.value = value
+        self.edges = []
+
+    def __str__(self):
+        return "Node: %d" % self.value
+
+
+class Graph:
+    def __init__(self, nodes=[]):
+        self.nodes = nodes
+
+    def add_node(self, value):
+        node = Node(value)
+        self.nodes.append(node)
+
+        return node
+
+    @staticmethod
+    def add_edge(a, b):
+        a.edges.append(b)
+
+    @staticmethod
+    def route_between_nodes(a, b):
+        if a is b:
+            return True
+
+        q = []
+        visited = set()
+        q.append(a)
+
+        while q:  # while non-empty
+            curr = q.pop(0)
+            for edge in curr.edges:
+                if edge is b:
+                    return True
+                if edge not in visited:
+                    q.append(edge)
+            visited.add(curr)
+
+        return False
+
+
+g = Graph()
+node_1 = g.add_node(1)
+node_2 = g.add_node(2)
+node_3 = g.add_node(3)
+node_4 = g.add_node(4)
+node_5 = g.add_node(5)
+g.add_edge(node_1, node_2)
+g.add_edge(node_1, node_3)
+g.add_edge(node_1, node_4)
+g.add_edge(node_2, node_3)
+g.add_edge(node_3, node_4)
+g.add_edge(node_4, node_5)
+
+u = node_1
+v = node_5
+if g.route_between_nodes(u, v):
+    print("There is a path from %s to %s" % (u, v))
+else:
+    print("There is no path from %s to %s" % (u, v))
+
+u = node_5
+v = node_1
+if g.route_between_nodes(u, v):
+    print("There is a path from %s to %s" % (u, v))
+else:
+    print("There is no path from %s to %s" % (u, v))