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Clone Graph

2024-07-10 01:57:47   228人阅读

题目

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
         /          \_/

方法

主要分两步：第一步创建所有的结点，第二步，创建结点的neighbors
/**
 * 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;
    	}
    	Map<Integer, UndirectedGraphNode> map = new HashMap<Integer, UndirectedGraphNode>();
    	Map<Integer, UndirectedGraphNode> graph = new HashMap<Integer, UndirectedGraphNode>();
    	Queue<UndirectedGraphNode> queue = new LinkedList<UndirectedGraphNode>();
    	queue.offer(node);
    	while(!queue.isEmpty()) {
    		UndirectedGraphNode temp = queue.poll();
    		
    		if (!map.containsKey(temp.label)) {
    			UndirectedGraphNode newTemp = new UndirectedGraphNode(temp.label);
    			graph.put(temp.label, temp);
    			map.put(temp.label, newTemp);
    		}
    		
    		for (UndirectedGraphNode neighbor : temp.neighbors) {
    			if (!map.containsKey(neighbor.label)) {
    				queue.offer(neighbor);
    			}
    		}
    	}
    	for (int label : graph.keySet()) {
    		UndirectedGraphNode temp = graph.get(label);
    		UndirectedGraphNode cloneTemp = map.get(temp.label);
			for (UndirectedGraphNode neighbor : temp.neighbors) {
				cloneTemp.neighbors.add(map.get(neighbor.label));
			}
    	}
    	return map.get(node.label);
    }
}


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