leetcode133. Clone Graph

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 #.

First node is labeled as 0. Connect node 0 to both nodes 1 and 2.
Second node is labeled as 1. Connect node 1 to node 2.
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         / \         \_/

public class CloneGraph {    //深搜 递归    public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {        if(node==null) return null;        Map<UndirectedGraphNode,UndirectedGraphNode> map = new HashMap<>();        return clone(node,map);    }    private UndirectedGraphNode clone(UndirectedGraphNode node, Map<UndirectedGraphNode, UndirectedGraphNode> map) {        if(node==null) return null;        //遍历过的节点会存放在map集合 (set集合)        if(map.containsKey(node)) {            return map.get(node);        }        //如果没有被遍历过        UndirectedGraphNode newNode = new UndirectedGraphNode(node.label);        map.put(node, newNode);        for(UndirectedGraphNode neighbour : node.neighbors) {            newNode.neighbors.add(clone(neighbour,map));        }        return newNode;    }    //深搜 非递归    public UndirectedGraphNode cloneGraph3(UndirectedGraphNode node) {        if(node==null) return null;        Map<UndirectedGraphNode,UndirectedGraphNode> map = new HashMap<>();        Stack<UndirectedGraphNode> stack = new Stack<>();        UndirectedGraphNode newHead = new UndirectedGraphNode(node.label);        map.put(node, newHead);        stack.push(node);        while(!stack.isEmpty()) {            UndirectedGraphNode tmp = stack.pop();            for(UndirectedGraphNode neighbour : tmp.neighbors) {                if(!map.containsKey(neighbour)) {                    UndirectedGraphNode copy = new UndirectedGraphNode(neighbour.label);                    map.put(neighbour, copy);                    map.get(tmp).neighbors.add(copy);                    stack.push(neighbour);                } else {                    map.get(tmp).neighbors.add(map.get(neighbour));                }            }        }        return newHead;    }    //广搜 使用队列实现    public UndirectedGraphNode cloneGraph2(UndirectedGraphNode node) {        if(node==null) return null;        Map<UndirectedGraphNode,UndirectedGraphNode> map = new HashMap<>();        Queue<UndirectedGraphNode> queue = new LinkedList<>();        UndirectedGraphNode newHead = new UndirectedGraphNode(node.label);        map.put(node,newHead);        queue.add(node);        while(!queue.isEmpty()) {            UndirectedGraphNode tmp = queue.poll();            for(UndirectedGraphNode neighbour : tmp.neighbors) {                if(!map.containsKey(neighbour)) {                    UndirectedGraphNode copy = new UndirectedGraphNode(neighbour.label);                    map.put(neighbour,copy);                    map.get(tmp).neighbors.add(copy);                    queue.add(neighbour);                } else {                    map.get(tmp).neighbors.add(map.get(neighbour));                }            }        }        return newHead;    }}class UndirectedGraphNode {    int label;    List<UndirectedGraphNode> neighbors;    UndirectedGraphNode(int x) { label = x; neighbors = new ArrayList<UndirectedGraphNode>(); }};