dfs

Route Between Two Nodes in Graph.py

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+"""
+Given a directed graph, design an algorithm to find out whether there is a route between two nodes.
+
+Example
+Given graph:
+
+A----->B----->C
+ \     |
+  \    |
+   \   |
+    \  v
+     ->D----->E
+for s = B and t = E, return true
+
+for s = D and t = C, return false
+"""
+__author__ = 'Daniel'
+
+
+class DirectedGraphNode:
+    def __init__(self, x):
+        self.label = x
+        self.neighbors = []
+
+
+class Solution(object):
+    def hasRoute(self, graph, s, t):
+        visited = set()
+        return self.dfs(s, t, visited)
+
+    def dfs(self, s, t, visited):
+        """pre-check"""
+        if s == t:
+            return True
+
+        visited.add(s)
+        for nbr in s.neighbors:
+            if nbr not in visited:
+                if self.dfs(nbr, t, visited):
+                    return True
+
+        return False
+