Added new problems

Author: shichao-an

clone_graph/solution.py

@@ -0,0 +1,43 @@
+"""
+Clone an undirected graph. Each node in the graph contains a label and a list
+of its neighbors.
+"""
+
+# Definition for a undirected graph node
+# class UndirectedGraphNode(object):
+#     def __init__(self, x):
+#         self.label = x
+#         self.neighbors = []
+
+class Solution(object):
+    def cloneGraph(self, node):
+        """
+        :type node: UndirectedGraphNode
+        :rtype: UndirectedGraphNode
+
+        BFS
+        """
+        if node is None:
+            return None
+        queue = []
+        start_cloned_node = UndirectedGraphNode(node.label)
+        visited = set()
+        # A dictionary that maps labels to cloned nodes
+        d = {node: start_cloned_node}
+        queue.append(node)
+        while queue:
+            node = queue.pop(0)
+            visited.add(node)
+            cloned_node = d[node]
+            cloned_neighbors = []
+            for neighbor in node.neighbors:
+                if neighbor not in visited:
+                    queue.append(neighbor)
+                if neighbor not in d:
+                    cloned_neighbor = UndirectedGraphNode(neighbor.label)
+                    d[neighbor] = cloned_neighbor
+                else:
+                    cloned_neighbor = d[neighbor]
+                cloned_neighbors.append(cloned_neighbor)
+            cloned_node.neighbors = cloned_neighbors
+        return start_cloned_node

clone_graph/solution2.py

@@ -0,0 +1,41 @@
+"""
+Clone an undirected graph. Each node in the graph contains a label and a list
+of its neighbors.
+"""
+
+# Definition for a undirected graph node
+# class UndirectedGraphNode(object):
+#     def __init__(self, x):
+#         self.label = x
+#         self.neighbors = []
+
+class Solution(object):
+    def cloneGraph(self, node):
+        """
+        :type node: UndirectedGraphNode
+        :rtype: UndirectedGraphNode
+
+        DFS
+        """
+        if node is None:
+            return None
+        self.visited = set()
+        cloned_node = UndirectedGraphNode(node.label)
+        self.d = {node: cloned_node}
+        self.visit(node)
+        return self.d[node]
+
+    def visit(self, node):
+        if node not in self.visited:
+            self.visited.add(node)
+            cloned_node = self.d[node]
+            cloned_neighbors = []
+            for neighbor in node.neighbors:
+                if neighbor not in self.d:
+                    cloned_neighbor = UndirectedGraphNode(neighbor.label)
+                    self.d[neighbor] = cloned_neighbor
+                else:
+                    cloned_neighbor = self.d[neighbor]
+                cloned_neighbors.append(cloned_neighbor)
+                self.visit(neighbor)
+            cloned_node.neighbors = cloned_neighbors