Clone Graph

Clone an undirected graph. Each node in the graph contains a label and a list of its neighbors.

Analysis

• 用一个hashmap用来记录visited过的node，node的label作为key(题目中已说明lable unique)，复制的node作为value
• 从原graph的一个node开始，首先复制一个和原node值一样的node
• 把这个复制的node和它的值放到map里去
• 然后遍历原node所有的neighbor，把每一个neibor都clone一遍，clone后返回的node作为新的neigbor
• base情况1：如果node为null，clone直接返回null
• base情况2：如果找到的node已经visited过了，那么直接找到对应的clone的node返回

Code

/**
 * Definition for undirected graph.
 * class UndirectedGraphNode {
 *     int label;
 *     List<UndirectedGraphNode> neighbors;
 *     UndirectedGraphNode(int x) { label = x; neighbors = new ArrayList<UndirectedGraphNode>(); }
 * };
 */
public class Solution {
    private HashMap<Integer, UndirectedGraphNode> map = new HashMap<>();
    public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {
        return clone(node);
    }

    private UndirectedGraphNode clone(UndirectedGraphNode node) {
        if (node == null) return null;

        if (map.containsKey(node.label)) {
            return map.get(node.label);
        }
        UndirectedGraphNode clone = new UndirectedGraphNode(node.label);
        map.put(clone.label, clone);
        for (UndirectedGraphNode neighbor : node.neighbors) {
            clone.neighbors.add(clone(neighbor));
        }
        return clone;
    }
}

Reference

Leetcode