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[leetcode]clone graph

admin 11月 11, 2020 0

题目描述

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  labeled as 0. Connect node 0 to both nodes 1 and 2.
2. Second node  labeled as 1. Connect node 1 to node 2.
3. Third node  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
     / 
     _/

代码


 * Definition for undirected graph.
 * class UndirectedGraphNode {
 *     int label;
 *     List<UndirectedGraphNode> neighbors;
 *     UndirectedGraphNode(int x) { label = x; neighbors = new ArrayList<UndirectedGraphNode>(); }
 * };
 */
public class Solution {
    //key为图节点的label，value为图节点
    private Map<Integer, UndirectedGraphNode> map = new HashMap<>();
    public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {
        if(node == null) return null;

        if(map.containsKey(node.label)) return map.get(node.label);

        UndirectedGraphNode clone = new UndirectedGraphNode(node.label);

        map.put(clone.label, clone);
        //DFS拷贝node的neighbors节点
        for(UndirectedGraphNode neighbor : node.neighbors){
            clone.neighbors.add(cloneGraph(neighbor));
        }

        return clone;
    }
}