Clone Graph

Change-Id: If70cd55492a20f1da193454f580ddfdb3d41126a

CloneGraph.java

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+/*
+ Author:     Andy, [email protected]
+ Date:       Jan 13, 2015
+ Problem:    Clone Graph
+ Difficulty: Medium
+ Source:     http://oj.leetcode.com/problems/clone-graph/
+ Notes:
+ Clone an undirected graph. Each node in the graph contains a label and a list of its neighbors.
+ 
+ OJ's undirected graph serialization:
+ Nodes are labeled from 0 to N - 1, where N is the total nodes in the graph.
+ We use # as a separator for each node, and , as a separator for each neighbor of the node.
+ As an example, consider the serialized graph {1,2#2#2}.
+ The graph has a total of three nodes, and therefore contains three parts as separated by #.
+ Connect node 0 to both nodes 1 and 2.
+ Connect node 1 to node 2.
+ Connect node 2 to node 2 (itself), thus forming a self-cycle.
+ Visually, the graph looks like the following:
+
+       1
+      / \
+     /   \
+    0 --- 2
+         / \
+         \_/
+
+ Solution: 1. DFS. 2. BFS.
+ */
+
+/**
+ * Definition for undirected graph.
+ * class UndirectedGraphNode {
+ *     int label;
+ *     List<UndirectedGraphNode> neighbors;
+ *     UndirectedGraphNode(int x) { label = x; neighbors = new ArrayList<UndirectedGraphNode>(); }
+ * };
+ */
+public class Solution {
+    public UndirectedGraphNode cloneGraph_1(UndirectedGraphNode node) {
+        HashMap<UndirectedGraphNode, UndirectedGraphNode> map = new HashMap<UndirectedGraphNode, UndirectedGraphNode>();
+        return cloneGraphRe(node, map);
+    }
+    public UndirectedGraphNode cloneGraphRe(UndirectedGraphNode node, HashMap<UndirectedGraphNode, UndirectedGraphNode> map) {
+        if (node == null) return null;
+        if (map.containsKey(node) == true) {
+            return map.get(node);
+        }
+        UndirectedGraphNode newnode = new UndirectedGraphNode(node.label);
+        map.put(node, newnode);
+        for (UndirectedGraphNode cur : node.neighbors) {
+            newnode.neighbors.add(cloneGraphRe(cur, map));
+        }
+        return newnode;
+    }
+    public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {
+        HashMap<UndirectedGraphNode, UndirectedGraphNode> map = new HashMap<UndirectedGraphNode, UndirectedGraphNode>();
+        Queue<UndirectedGraphNode> queue = new LinkedList<UndirectedGraphNode>();
+        if (node == null) return null;
+        queue.offer(node);
+        map.put(node, new UndirectedGraphNode(node.label));
+        while (queue.isEmpty() == false) {
+            UndirectedGraphNode cur = queue.poll();
+            for (UndirectedGraphNode neighbor : cur.neighbors) {
+                if (map.containsKey(neighbor) == false) {
+                    UndirectedGraphNode newnode = new UndirectedGraphNode(neighbor.label);
+                    map.put(neighbor, newnode);
+                    queue.offer(neighbor);
+                }
+                map.get(cur).neighbors.add(map.get(neighbor));
+            }
+        }
+        return map.get(node);
+    }
+}