CloneGraph.java

/*
 Author:     Andy, nkuwjg@gmail.com
 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);
    }
}