精通算法系列-复制图形

原题如下：

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

意思就是:给定一个没有方向的图形,你要做的就是复制一个一样的图形

答案如下：

public class Solution {    public HashMap<Integer, UndirectedGraphNode> map = new HashMap<Integer, UndirectedGraphNode>();    public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {        if(node == null) return null;        if(map.containsKey(node.label)) return map.get(node.label);        UndirectedGraphNode newNode = new UndirectedGraphNode(node.label);        map.put(newNode.label, newNode);        for(UndirectedGraphNode neighbor : node.neighbors) {            newNode.neighbors.add(cloneGraph(neighbor));        }        return newNode;    }}

核心思路:遍历每一个节点，并把当前节点有的再重新添加到新的图形当中