Search Graph Nodes

最新推荐文章于 2022-07-11 07:36:00 发布

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最新推荐文章于 2022-07-11 07:36:00 发布

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分类专栏： leetcode 文章标签： github mac python stack overflow 遍历

本文链接：https://blog.youkuaiyun.com/sinat_32547403/article/details/77985620

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本文介绍了一种在无向图中寻找具有特定目标值的最近节点的方法。使用队列和集合来跟踪已访问节点，并避免重复访问。适用于Java和Python实现。

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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.

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 the a node
     */
    public UndirectedGraphNode searchNode(ArrayList<UndirectedGraphNode> graph,
                                          Map<UndirectedGraphNode, Integer> values,
                                          UndirectedGraphNode node,
                                          int target) {
        // Write your code here
        if (node == null || values == null) {
            return null;
        }
        if (values.get(node) == target) {
            return node;
        }
        Queue<UndirectedGraphNode> queue = new LinkedList<>();
        Set<UndirectedGraphNode> set = new HashSet<>();
        queue.offer(node);
        set.add(node);
        while (!queue.isEmpty()) {
            UndirectedGraphNode root = queue.poll();
            for (UndirectedGraphNode nei : root.neighbors) {
                if (values.get(nei) == target) {
                    return nei;
                }
                if (set.contains(nei)) {
                    continue;
                } else {
                    set.add(nei);
                    queue.offer(nei);
                }
            }
        }
        return null;
    }
}

python

from Queue import Queue

# Definition for a undirected graph node
# class UndirectedGraphNode:
#     def __init__(self, x):
#         self.label = x
#         self.neighbors = []

class Solution:
    # @param {UndirectedGraphNode[]} graph a list of undirected graph node
    # @param {dict} values a dict, <UndirectedGraphNode, (int)value>
    # @param {UndirectedGraphNode} node an Undirected graph node
    # @param {int} target an integer
    # @return {UndirectedGraphNode} a node
    def searchNode(self, graph, values, node, target):
        # Write your code here
        if node is None or graph is None or values is None:
            return None
        if values[node] == target:
            return node
            
        queue = Queue()
        queue.put(node)
        arr = set([node])
        while not queue.empty(): 
            n = queue.get()
            for root in n.neighbors:
                if values[root] == target:
                    return root
                if root in arr:
                    continue
                else:
                    arr.add(root)
                    queue.put(root)
        return None