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  • Java for LeetCode 133 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
             /
             \_/
    解题思路:

    BFS或DFS均可做出,BFS的JAVA实现如下:

        public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {
    		if (node == null)
    			return null;
    		Queue<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.poll();
    			List<UndirectedGraphNode> currNeighbors = 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;
        }
    

     DFS 实现如下:

    	Map<UndirectedGraphNode, UndirectedGraphNode> map = new HashMap<UndirectedGraphNode, UndirectedGraphNode>();
    
    	public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {
    		if (node == null)
    			return null;
    		if (map.containsKey(node))
    			return map.get(node);
    		UndirectedGraphNode newHead = new UndirectedGraphNode(node.label);
    		map.put(node, newHead);
    		for (UndirectedGraphNode aNeighbor : node.neighbors)
    			newHead.neighbors.add(cloneGraph(aNeighbor));
    		return newHead;
    	}
    
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  • 原文地址:https://www.cnblogs.com/tonyluis/p/4545763.html
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