leetcode [Clone Graph] Java-优快云博客

本文链接：https://blog.youkuaiyun.com/crystal_tyan/article/details/43413569

本文介绍了一种无向图的序列化方法，使用特定符号分隔节点及邻居，并通过深度优先搜索实现图的深拷贝。利用HashMap记录已访问节点，避免重复拷贝。

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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:

题意很简单，就是深度复制，我选择了直接new。

至于遍历，在这个DFS比BFS方便，直接递归就可以了。

记录的话用了HashMap，注意还要储存node的值。

/**
 * Definition for undirected graph.
 * class UndirectedGraphNode {
 *     int label;
 *     List<UndirectedGraphNode> neighbors;
 *     UndirectedGraphNode(int x) { label = x; neighbors = new ArrayList<UndirectedGraphNode>(); }
 * };
 */
import java.util.HashMap;
public class Solution {
    public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {
        HashMap<Integer, UndirectedGraphNode> record = new HashMap<Integer, UndirectedGraphNode>();
        return clone(node, record);
    }
    private UndirectedGraphNode clone(UndirectedGraphNode node, HashMap<Integer, UndirectedGraphNode> record) {
        if(node == null) return node;
        if(record.containsKey(node.label)) return record.get(node.label);
        UndirectedGraphNode snode = new UndirectedGraphNode(node.label);
        record.put(node.label, snode);
        for (UndirectedGraphNode dnode : node.neighbors) {
            snode.neighbors.add(clone(dnode, record));
        }
        return snode;
    }
}