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  • 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 #.

    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
             / 
             \_/
    很简单,BFS遍历,加上Map来保存label和节点地址
    /**
     * 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(UndirectedGraphNode node) {
            if(node == null)
                return null;
     
            LinkedList<UndirectedGraphNode> queue = new LinkedList<UndirectedGraphNode>();
            HashMap<UndirectedGraphNode, UndirectedGraphNode> map = 
                                       new HashMap<UndirectedGraphNode,UndirectedGraphNode>();
     
            UndirectedGraphNode newHead = new UndirectedGraphNode(node.label);
     
            queue.add(node);
            map.put(node, newHead);
     
            while(!queue.isEmpty()){
                UndirectedGraphNode curr = queue.pop();
                ArrayList<UndirectedGraphNode> currNeighbors = (ArrayList)curr.neighbors; 
     
                for(UndirectedGraphNode aNeighbor: currNeighbors){
                    if(!map.containsKey(aNeighbor)){
                        UndirectedGraphNode copy = new UndirectedGraphNode(aNeighbor.label);
                        map.put(aNeighbor,copy);
                        map.get(curr).neighbors.add(copy);
                        queue.add(aNeighbor);
                    }else{
                        map.get(curr).neighbors.add(map.get(aNeighbor));
                    }
                }
     
            }
            return newHead;
            
        }
    }
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  • 原文地址:https://www.cnblogs.com/qionghua520/p/4385279.html
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