Lintcode 618. Search Graph Nodes

Given a undirected graph, a node and a target, return the nearest node to given node which value of it is target, return NULL if you can't find.

There is a mapping store the nodes' values in the given parameters.

Example

Example 1:

Input:
{1,2,3,4#2,1,3#3,1#4,1,5#5,4}
[3,4,5,50,50]
1
50
Output:
4
Explanation:
2------3  5
 \     |  | 
  \    |  |
   \   |  |
    \  |  |
      1 --4
Give a node 1, target is 50

there a hash named values which is [3,4,10,50,50], represent:
Value of node 1 is 3
Value of node 2 is 4
Value of node 3 is 10
Value of node 4 is 50
Value of node 5 is 50

Return node 4

Example 2:

Input:
{1,2#2,1}
[0,1]
1
1
Output:
2

Notice

It's guaranteed there is only one available solution

Code (Java):

/**
 * Definition for graph node.
 * class UndirectedGraphNode {
 *     int label;
 *     ArrayList<UndirectedGraphNode> neighbors;
 *     UndirectedGraphNode(int x) { 
 *         label = x; neighbors = new ArrayList<UndirectedGraphNode>(); 
 *     }
 * };
 */


public class Solution {
    /*
     * @param graph: a list of Undirected graph node
     * @param values: a hash mapping, <UndirectedGraphNode, (int)value>
     * @param node: an Undirected graph node
     * @param target: An integer
     * @return: a node
     */
    public UndirectedGraphNode searchNode(ArrayList<UndirectedGraphNode> graph,
                                          Map<UndirectedGraphNode, Integer> values,
                                          UndirectedGraphNode node,
                                          int target) {
        // BFS
        //
        Queue<UndirectedGraphNode> queue = new LinkedList<>();
        Set<UndirectedGraphNode> visited = new HashSet<>();

        // pre-process the graph
        //
        Map<UndirectedGraphNode, List<UndirectedGraphNode>> adjList  = new HashMap<>();
        for (UndirectedGraphNode e : graph) {
            adjList.put(e, e.neighbors);
        }

        queue.offer(node);
        visited.add(node);

        while (!queue.isEmpty()) {
            UndirectedGraphNode curNode = queue.poll();
            if (values.get(curNode) == target) {
                return curNode;
            }

            for (UndirectedGraphNode neighbor : adjList.get(curNode)) {
                if (!visited.contains(neighbor)) {
                    queue.offer(neighbor);
                    visited.add(neighbor);
                }
            }
        }

        return null;
    }
}