LeetCode-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 #.

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
         / 
         \_/


Solution:

/**
 * 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<UndirectedGraphNode,UndirectedGraphNode> cloneMap = new HashMap<UndirectedGraphNode,UndirectedGraphNode>();
        Set<UndirectedGraphNode> visited = new HashSet<UndirectedGraphNode>();
        cloneMap.put(node, new UndirectedGraphNode(node.label)); 
        
        return cloneGraphRecur(node,cloneMap,visited);
    }

    public UndirectedGraphNode cloneGraphRecur(UndirectedGraphNode cur, Map<UndirectedGraphNode,UndirectedGraphNode> cloneMap, Set<UndirectedGraphNode> visited){
        UndirectedGraphNode curClone = cloneMap.get(cur);
        visited.add(cur);

        //Clone all the neighbors of cur node.
        for (int i=0;i<cur.neighbors.size();i++){
            UndirectedGraphNode neigh = cur.neighbors.get(i);
            if (cloneMap.containsKey(neigh)){
                curClone.neighbors.add(cloneMap.get(neigh));
            } else {
                UndirectedGraphNode neighClone = new UndirectedGraphNode(neigh.label);
                cloneMap.put(neigh,neighClone);
                curClone.neighbors.add(neighClone);
            }
        }

        //Visit all unvisited neighbors of cur node.
        for (int i=0;i<cur.neighbors.size();i++)
            if (!visited.contains(cur.neighbors.get(i)))
                cloneGraphRecur(cur.neighbors.get(i),cloneMap,visited);

        return curClone;
    }
            
}

Solution (BFS):

/**
 * 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<UndirectedGraphNode,UndirectedGraphNode> cloneMap = new HashMap<UndirectedGraphNode,UndirectedGraphNode>();
        List<UndirectedGraphNode> visited = new ArrayList<UndirectedGraphNode>();
        cloneMap.put(node, new UndirectedGraphNode(node.label)); 
        visited.add(node);
        int index = 0;
        while (index<visited.size()){
            UndirectedGraphNode cur = visited.get(index);
            UndirectedGraphNode curClone = cloneMap.get(cur);

            //Clone all the neighbors of cur node.
            for (int i=0;i<cur.neighbors.size();i++){
                UndirectedGraphNode neigh = cur.neighbors.get(i);
            if (cloneMap.containsKey(neigh)){
                    curClone.neighbors.add(cloneMap.get(neigh));
                } else {
                    UndirectedGraphNode neighClone = new UndirectedGraphNode(neigh.label);
                    cloneMap.put(neigh,neighClone);
                curClone.neighbors.add(neighClone);
                visited.add(neigh);
                }
            }

            index++;
        }
        
        return cloneMap.get(node);


    }            
}