Question Definition
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
/ \
\_/
Java Solution
/**
* Definition for undirected graph.
* class UndirectedGraphNode {
* int label;
* List<UndirectedGraphNode> neighbors;
* UndirectedGraphNode(int x) { label = x; neighbors = new ArrayList<UndirectedGraphNode>(); }
* };
*/
public class Solution {
private HashMap<Integer, UndirectedGraphNode> map = new HashMap<>();
public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {
return clone(node);
}
private UndirectedGraphNode clone(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);
for (UndirectedGraphNode neighbor : node.neighbors) {
clone.neighbors.add(clone(neighbor));
}
return clone;
}
}
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