Clone Graph @LeetCode

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 uniquely.

We use # as a separator for each node, and , as a separator for node label and each neighbor of the node.

As an example, consider the serialized graph {0,1,2#1,2#2,2}.

The graph has a total of three nodes, and therefore contains three parts as separated by #.

1. First node is labeled as 0. Connect node 0 to both nodes 1 and 2.
2. Second node is labeled as 1. Connect node 1 to node 2.
3. Third node is labeled as 2. Connect node 2 to node 2 (itself), thus forming a self-cycle.

Visually, the graph looks like the following:

       1
      / \
     /   \
    0 --- 2
         / \
         \_/

	package leetcode;
	import java.util.ArrayList;
	import java.util.HashMap;
	import java.util.LinkedList;
	import java.util.Queue;
	/**
	* Graph BFS || DFS 主要是记得要用HashMap 来保存 original 和 copy 的关系
	* @author jeffwan
	* @date May 18, 2014
	*/
	public class CloneGraph {
	// BFS
	public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {
	if (node == null) {
	return null;
	}
	Queue<UndirectedGraphNode> queue = new LinkedList<UndirectedGraphNode>();
	HashMap<UndirectedGraphNode, UndirectedGraphNode> map = new HashMap<UndirectedGraphNode, UndirectedGraphNode>();
	UndirectedGraphNode copy = new UndirectedGraphNode(node.label);
	map.put(node, copy);
	queue.offer(node);
	while (!queue.isEmpty()) {
	UndirectedGraphNode current = queue.poll();
	for (int i = 0; i < current.neighbors.size(); i++) {
	if (!map.containsKey(current.neighbors.get(i))) {
	copy = new UndirectedGraphNode(current.neighbors.get(i).label);
	map.put(current.neighbors.get(i), copy);
	queue.offer(current.neighbors.get(i));
	}
	//clone neighbours
	map.get(current).neighbors.add(map.get(current.neighbors.get(i)));
	}
	}
	return map.get(node);
	}
	//DFS - recursive
	public UndirectedGraphNode cloneGraph2(UndirectedGraphNode node) {
	if(node == null)
	return null;
	HashMap<UndirectedGraphNode, UndirectedGraphNode> map = new HashMap<UndirectedGraphNode, UndirectedGraphNode>();
	UndirectedGraphNode copy = new UndirectedGraphNode(node.label);
	map.put(node,copy);
	helper(node,map);
	return copy;
	}
	private void helper(UndirectedGraphNode node,
	HashMap<UndirectedGraphNode, UndirectedGraphNode> map) {
	for (int i = 0; i < node.neighbors.size(); i++) {
	UndirectedGraphNode cur = node.neighbors.get(i);
	if (!map.containsKey(cur)) {
	UndirectedGraphNode copy = new UndirectedGraphNode(cur.label);
	map.put(cur, copy);
	helper(cur, map);
	}
	map.get(node).neighbors.add(map.get(cur));
	}
	}
	class UndirectedGraphNode {
	int label;
	ArrayList<UndirectedGraphNode> neighbors;
	UndirectedGraphNode(int x) {
	label = x;
	neighbors = new ArrayList<UndirectedGraphNode>();
	}
	};
	}

view raw CloneGraph.java hosted with ❤ by GitHub