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Author: Chris Wu

problems/is-graph-bipartite.py

@@ -0,0 +1,38 @@
+from collections import defaultdict
+
+class Solution(object):
+    def isBipartite(self, graph):
+        if not graph: return True
+        
+        A, B = set(), set()
+        stack = []
+        
+        for node in xrange(len(graph)): #[1]
+            #check if visited, if not start DFS by putting it to stack
+            if node not in A and node not in B:
+                stack.append(node)
+                A.add(node)
+            
+            while stack: #[0]
+                n = stack.pop()
+                if n in A:
+                    for nei in graph[n]:
+                        if nei in A: return False
+                        if nei not in B:
+                            stack.append(nei)
+                            B.add(nei)
+                elif n in B:
+                    for nei in graph[n]:
+                        if nei in B: return False
+                        if nei not in A:
+                            stack.append(nei)
+                            A.add(nei)
+        return True
+"""
+Use DFS to travserse each node [0]
+If the node is in A, all its children should be in B.
+If the node is in B, all its children should be in A.
+
+Not necessary all the nodes in graph are connected. [1]
+So we still need to loop the node to check if it is visited.
+"""