Clone an undirected graph. Each node in the graph contains a label and a list of its neighbors.OJ's undirected graph serialization:Nodes are labeled uniquely.We use # as a separator for each node, and , as a separator for node label and each neighbor of the node.As an example, consider the serialized graph {0,1,2#1,2#2,2}.The graph has a total of three nodes, and therefore contains three parts as separated by #.First node is labeled as 0. Connect node 0 to both nodes 1 and 2.Second node is labeled as 1. Connect node 1 to node 2.Third node is labeled as 2. Connect node 2 to node 2 (itself), thus forming a self-cycle.Visually, the graph looks like the following:       1      / \     /   \    0 --- 2         / \         \_/

广度优先搜索法

思路

用一个hashmap将原节点和复制的节点映射起来, 因为hashmap的存在 可以不用记录visited, 因为凡是便利过的都在map中

复杂度

一次便利时间O(n) 空间O(n)

代码

public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {    if (node == null) {        return null;    }    HashMap<UndirectedGraphNode, UndirectedGraphNode> map = new HashMap<UndirectedGraphNode, UndirectedGraphNode>();    map.put(node, new UndirectedGraphNode(node.label));    Queue<UndirectedGraphNode> queue = new LinkedList<UndirectedGraphNode>();    queue.offer(node);    while (!queue.isEmpty()) {        UndirectedGraphNode cur = queue.poll();        for (UndirectedGraphNode tem : cur.neighbors) {if (!map.containsKey(tem)) {    queue.offer(tem);    map.put(tem, new UndirectedGraphNode(tem.label));}map.get(cur).neighbors.add(map.get(tem));        }    }    return map.get(node);}

深度优先搜索

复杂度

时间O(n) 空间O(n)

代码

public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {    if (node == null) {        return null;    }    HashMap<UndirectedGraphNode, UndirectedGraphNode> map = new HashMap<UndirectedGraphNode, UndirectedGraphNode>();    map.put(node, new UndirectedGraphNode(node.label));    dfs(map, node);    return map.get(node);}public void dfs(HashMap<UndirectedGraphNode, UndirectedGraphNode> map, UndirectedGraphNode node) {    if (node == null) {        return;    }    for (UndirectedGraphNode cur : node.neighbors) {        if (!map.containsKey(cur)) {map.put(cur, new UndirectedGraphNode(cur.label));dfs(map, cur);        }        map.get(node).neighbors.add(map.get(cur));    }}