算法练习笔记（十三）——图的克隆

在leetcode上多为解答题，然而偶尔一次的定义型题目也是十分的让人耳目一新

题目地址：https://leetcode.com/problems/clone-graph/#/description

题目：Clone Graph

描述：

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         / \         \_/

本题中对一个图做了这样的定义：

将结点之间用#隔开，相邻点用，隔开

由此求在给定一个结点的情况下，利用映射进行此结点的映射克隆

主要的困难其实在于对于题解的理解，和对于map结构的运用

解答如下：

/** * Definition for undirected graph. * struct UndirectedGraphNode { *     int label; *     vector<UndirectedGraphNode *> neighbors; *     UndirectedGraphNode(int x) : label(x) {}; * }; */class Solution {public:    UndirectedGraphNode *cloneGraph(UndirectedGraphNode *node) {       if(node == NULL)return NULL;       if(mymap.find(node) == mymap.end()){                                //mymap.find(node) == mymap.end();           mymap[node] = new UndirectedGraphNode(node -> label);           for(UndirectedGraphNode * h : node -> neighbors){               mymap[node] -> neighbors.push_back(cloneGraph(h));   //遍历           }       }       return mymap[node];    }private:    map<UndirectedGraphNode *, UndirectedGraphNode *> mymap;};