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 #.

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
         /          \_/

 1 /**
 2  * Definition for undirected graph.
 3  * class UndirectedGraphNode {
 4  *     int label;
 5  *     List<UndirectedGraphNode> neighbors;
 6  *     UndirectedGraphNode(int x) { label = x; neighbors = new ArrayList<UndirectedGraphNode>(); }
 7  * };
 8  */
 9 public class Solution {
10     public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {
11         if (node == null) return null;
12         HashMap<UndirectedGraphNode, UndirectedGraphNode> map = new HashMap<UndirectedGraphNode, UndirectedGraphNode>();
13         LinkedList<UndirectedGraphNode> queue = new LinkedList<UndirectedGraphNode>();
14         queue.offer(node);
15         UndirectedGraphNode copy = new UndirectedGraphNode(node.label);
16         map.put(node, copy);
17         while (!queue.isEmpty()) {
18             UndirectedGraphNode cur = queue.poll();
19             for (int i=0; i<cur.neighbors.size(); i++) {
20                 if (!map.containsKey(cur.neighbors.get(i))) {
21                     queue.offer(cur.neighbors.get(i));
22                     UndirectedGraphNode neighborCopy = new UndirectedGraphNode(cur.neighbors.get(i).label);
23                     map.put(cur.neighbors.get(i), neighborCopy);
24                 }
25                 map.get(cur).neighbors.add(map.get(cur.neighbors.get(i)));
26             }
27         }
28         return map.get(node);
29     }
30 }

 1 public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {
 2     if(node == null)
 3         return null;
 4     LinkedList<UndirectedGraphNode> stack = new LinkedList<UndirectedGraphNode>();
 5     HashMap<UndirectedGraphNode, UndirectedGraphNode> map = new HashMap<UndirectedGraphNode, UndirectedGraphNode>();
 6     stack.push(node);
 7     UndirectedGraphNode copy = new UndirectedGraphNode(node.label);
 8     map.put(node,copy);
 9     while(!stack.isEmpty())
10     {
11         UndirectedGraphNode cur = stack.pop();
12         for(int i=0;i<cur.neighbors.size();i++)
13         {
14             if(!map.containsKey(cur.neighbors.get(i)))
15             {
16                 copy = new UndirectedGraphNode(cur.neighbors.get(i).label);
17                 map.put(cur.neighbors.get(i),copy);
18                 stack.push(cur.neighbors.get(i));
19             }
20             map.get(cur).neighbors.add(map.get(cur.neighbors.get(i)));
21         }
22     }
23     return map.get(node);
24 }

 1 public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {
 2     if(node == null)
 3         return null;
 4     HashMap<UndirectedGraphNode, UndirectedGraphNode> map = new HashMap<UndirectedGraphNode, UndirectedGraphNode>();
 5     UndirectedGraphNode copy = new UndirectedGraphNode(node.label);
 6     map.put(node,copy);
 7     helper(node,map);
 8     return copy;
 9 }
10 private void helper(UndirectedGraphNode node, HashMap<UndirectedGraphNode, UndirectedGraphNode> map)
11 {
12     for(int i=0;i<node.neighbors.size();i++)
13     { 
14         UndirectedGraphNode cur = node.neighbors.get(i);
15         if(!map.containsKey(cur))
16         {
17             UndirectedGraphNode copy = new UndirectedGraphNode(cur.label);
18             map.put(cur,copy);
19             helper(cur,map);
20         }
21         map.get(node).neighbors.add(map.get(cur));
22     }
23 }