_133_CloneGraph.java

package leetcode_1To300;

import java.util.*;

/**
 * 本代码来自 Cspiration，由 @Cspiration 提供
 * 题目来源：http://leetcode.com
 * - Cspiration 致力于在 CS 领域内帮助中国人找到工作，让更多海外国人受益
 * - 现有课程：Leetcode Java 版本视频讲解（1-900题）（上）（中）（下）三部
 * - 算法基础知识（上）（下）两部；题型技巧讲解（上）（下）两部
 * - 节省刷题时间，效率提高2-3倍，初学者轻松一天10题，入门者轻松一天20题
 * - 讲师：Edward Shi
 * - 官方网站：https://cspiration.com
 * - 版权所有，转发请注明出处
 */
public class _133_CloneGraph {
    /**
     * 133. Clone Graph
     * time : O(m + n) m : nodes n : edges
     * space : O(m)
     */

    HashMap<UndirectedGraphNode, UndirectedGraphNode> map = new HashMap<>();

    public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {
        return helper(node);
    }
    public UndirectedGraphNode helper(UndirectedGraphNode node) {
        if (node == null) return null;
        if (map.containsKey(node)) return map.get(node);
        UndirectedGraphNode dup = new UndirectedGraphNode(node.label);
        map.put(node, dup);
        for (UndirectedGraphNode neighboer : node.neighbors) {
            UndirectedGraphNode clone = helper(neighboer);
            dup.neighbors.add(clone);
        }
        return dup;
    }

    public UndirectedGraphNode cloneGraph2(UndirectedGraphNode node) {
        if (node == null) return node;
        List<UndirectedGraphNode> nodes = getNodes(node);
        HashMap<UndirectedGraphNode, UndirectedGraphNode> map = new HashMap<>();

        for (UndirectedGraphNode cur : nodes) {
            map.put(cur, new UndirectedGraphNode(cur.label));
        }
        for (UndirectedGraphNode cur : nodes) {
            UndirectedGraphNode newNode = map.get(cur);
            for (UndirectedGraphNode neighbor : cur.neighbors) {
                newNode.neighbors.add(map.get(neighbor));
            }
        }
        return map.get(node);
    }

    public List<UndirectedGraphNode> getNodes(UndirectedGraphNode node) {
        Queue<UndirectedGraphNode> queue = new LinkedList<>();
        HashSet<UndirectedGraphNode> set = new HashSet<>();
        queue.offer(node);
        set.add(node);

        while (!queue.isEmpty()) {
            UndirectedGraphNode cur = queue.poll();
            for (UndirectedGraphNode neighbor : cur.neighbors) {
                if (!set.contains(neighbor)) {
                    set.add(neighbor);
                    queue.offer(neighbor);
                }
            }
        }
        return new ArrayList<>(set);
    }
}