[LeetCode] Clone Graph

Clone Graph

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 #.

1. First node is labeled as 0. Connect node 0 to both nodes 1 and 2.
2. Second node is labeled as 1. Connect node 1 to node 2.
3. 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         / \         \_/

解题思路：

题意为拷贝图。我们可以用一个map来存储新图的标签到节点指针的映射关系。同时，用一个队列来存储待确定邻居的节点（原图节点指针，因为我们通过指针标签很容易找到新图节点指针）。

/** * 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;        }        map<int, UndirectedGraphNode*> nodeMap; //存的是新图的标签到节点指针对        queue<UndirectedGraphNode*> nodeQ;      //存的是原图的节点指针                UndirectedGraphNode* newNode = new UndirectedGraphNode(node->label);        nodeMap[node->label] = newNode;        nodeQ.push(node);                while(!nodeQ.empty()){            UndirectedGraphNode* n = nodeQ.front();            nodeQ.pop();            for(int i=0; i<n->neighbors.size(); i++){                if(nodeMap.find(n->neighbors[i]->label) == nodeMap.end()){                    nodeMap[n->neighbors[i]->label] = new UndirectedGraphNode(n->neighbors[i]->label);                    nodeQ.push(n->neighbors[i]);                }                nodeMap[n->label]->neighbors.push_back(nodeMap[n->neighbors[i]->label]);            }        }                return newNode;    }};