LeetCode-Clone Graph

LiBlog發表於2015-01-05
LeetCode

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:
 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 
13         Map<UndirectedGraphNode,UndirectedGraphNode> cloneMap = new HashMap<UndirectedGraphNode,UndirectedGraphNode>();
14         Set<UndirectedGraphNode> visited = new HashSet<UndirectedGraphNode>();
15         cloneMap.put(node, new UndirectedGraphNode(node.label)); 
16         
17         return cloneGraphRecur(node,cloneMap,visited);
18     }
19 
20     public UndirectedGraphNode cloneGraphRecur(UndirectedGraphNode cur, Map<UndirectedGraphNode,UndirectedGraphNode> cloneMap, Set<UndirectedGraphNode> visited){
21         UndirectedGraphNode curClone = cloneMap.get(cur);
22         visited.add(cur);
23 
24         //Clone all the neighbors of cur node.
25         for (int i=0;i<cur.neighbors.size();i++){
26             UndirectedGraphNode neigh = cur.neighbors.get(i);
27             if (cloneMap.containsKey(neigh)){
28                 curClone.neighbors.add(cloneMap.get(neigh));
29             } else {
30                 UndirectedGraphNode neighClone = new UndirectedGraphNode(neigh.label);
31                 cloneMap.put(neigh,neighClone);
32                 curClone.neighbors.add(neighClone);
33             }
34         }
35 
36         //Visit all unvisited neighbors of cur node.
37         for (int i=0;i<cur.neighbors.size();i++)
38             if (!visited.contains(cur.neighbors.get(i)))
39                 cloneGraphRecur(cur.neighbors.get(i),cloneMap,visited);
40 
41         return curClone;
42     }
43             
44 }

Solution (BFS):

 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 
13         Map<UndirectedGraphNode,UndirectedGraphNode> cloneMap = new HashMap<UndirectedGraphNode,UndirectedGraphNode>();
14         List<UndirectedGraphNode> visited = new ArrayList<UndirectedGraphNode>();
15         cloneMap.put(node, new UndirectedGraphNode(node.label)); 
16         visited.add(node);
17         int index = 0;
18         while (index<visited.size()){
19             UndirectedGraphNode cur = visited.get(index);
20             UndirectedGraphNode curClone = cloneMap.get(cur);
21 
22             //Clone all the neighbors of cur node.
23             for (int i=0;i<cur.neighbors.size();i++){
24                 UndirectedGraphNode neigh = cur.neighbors.get(i);
25             if (cloneMap.containsKey(neigh)){
26                     curClone.neighbors.add(cloneMap.get(neigh));
27                 } else {
28                     UndirectedGraphNode neighClone = new UndirectedGraphNode(neigh.label);
29                     cloneMap.put(neigh,neighClone);
30                 curClone.neighbors.add(neighClone);
31                 visited.add(neigh);
32                 }
33             }
34 
35             index++;
36         }
37         
38         return cloneMap.get(node);
39 
40 
41     }            
42 }

 

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