clone graph - Teeeeeebag/LeetCode GitHub Wiki

1. Pay attention to the place where you update the hash map

public class Solution {
    private HashMap<UndirectedGraphNode, UndirectedGraphNode> hm = new HashMap<>();
    public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {
        if(node == null){
            return null;
        }
        if (hm.containsKey(node)){
            return hm.get(node);
        }
        hm.put(node, n); // The place of this statement is important
                         // Initially, I put it before return, it will run into infinite loop!
        UndirectedGraphNode n = new UndirectedGraphNode(node.label);
        for (UndirectedGraphNode crt : node.neighbors){
            n.neighbors.add(cloneGraph(crt));
        }
        
        return n;
    }
}