Leetcode 133. Clone Graph

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题目:

Clone an undirected graph. Each node in the graph contains a label and a list of its neighbors.

/**
 * Definition for undirected graph.
 * class UndirectedGraphNode {
 *     int label;
 *     List neighbors;
 *     UndirectedGraphNode(int x) { label = x; neighbors = new ArrayList(); }
 * };
 */

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
/ \
\_/

DFS:

public class Solution {
    private Map<Integer, UndirectedGraphNode> map;
    public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {
        map = new HashMap<>();
        return cloneNode(node);
    }
    private UndirectedGraphNode cloneNode(UndirectedGraphNode node) {
        if(node == null) return null;
        if(map.containsKey(node.label)) return map.get(node.label);
        UndirectedGraphNode ans = new UndirectedGraphNode(node.label);
        map.put(node.label, ans);
        for(UndirectedGraphNode p: node.neighbors) ans.neighbors.add(cloneNode(p));
        return ans;
    }
}

BFS:

public class Solution {
    public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {
        if(node == null) return null;
        Map map = new HashMap<>();
        Queue queue = new LinkedList<>();
        UndirectedGraphNode ans = new UndirectedGraphNode(node.label);
        map.put(node.label, ans);
        queue.add(node);
        while(!queue.isEmpty())
        {
            UndirectedGraphNode t = queue.poll();
            for(UndirectedGraphNode p: t.neighbors)
            {
                if(!map.containsKey(p.label))
                {
                    map.put(p.label, new UndirectedGraphNode(p.label));
                    queue.offer(p);
                }
                map.get(t.label).neighbors.add(map.get(p.label));
            }
        }
        return ans;
    }
}

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