[LintCode] 618 Search Graph Nodes 解题报告

 1 /**
 2  * Definition for graph node.
 3  * class UndirectedGraphNode {
 4  *     int label;
 5  *     ArrayList<UndirectedGraphNode> neighbors;
 6  *     UndirectedGraphNode(int x) { 
 7  *         label = x; neighbors = new ArrayList<UndirectedGraphNode>(); 
 8  *     }
 9  * };
10  */
11 public class Solution {
12     /**
13      * @param graph a list of Undirected graph node
14      * @param values a hash mapping, <UndirectedGraphNode, (int)value>
15      * @param node an Undirected graph node
16      * @param target an integer
17      * @return the a node
18      */
19     public UndirectedGraphNode searchNode(ArrayList<UndirectedGraphNode> graph,
20                                           Map<UndirectedGraphNode, Integer> values,
21                                           UndirectedGraphNode node,
22                                           int target) {
23         // Write your code here
24         if (graph == null) return ret;
25         UndirectedGraphNode ret = null;
26         Set<UndirectedGraphNode> set = new HashSet<UndirectedGraphNode>();
27 
28         Queue<UndirectedGraphNode> queue = new LinkedList<UndirectedGraphNode>();
29         queue.offer(node);
30         while (!queue.isEmpty()) {
31             UndirectedGraphNode t = queue.poll();
32             if (values.get(t) == target) {
33                 return t;
34             }
35             for (UndirectedGraphNode n: t.neighbors) {
36                 if (!set.contains(n)) {
37                     set.add(n);
38                     queue.offer(n);
39                 }
40             }
41         }
42         return null;
43     }
44 }