LeetCode: Clone Graph [133]

【题目】

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
         / \
         \_/

【题意】

    复制无向图。无向图中每个点有一个值唯一的label和邻接节点的label集合

【思路】

    DFS或者BFS遍历无向图完成赋值
    【注意】本题中使用malloc创建节点会报RUNTIME ERROR错误，必须用new创建节点

    

【代码】

/**
 * 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;
        
        queue<UndirectedGraphNode*> qe;
        queue<UndirectedGraphNode*> qe_copy;
        map<int, UndirectedGraphNode*> createdMap;      //已经复制的节点
        
        //创建第一个节点
        //注意本题使用(UndirectedGraphNode*)malloc(sizeof(UndirectedGraphNode))会RUNTIME ERROR
        UndirectedGraphNode * newFirstNode = new UndirectedGraphNode(node->label);
        qe.push(node);
        qe_copy.push(newFirstNode);
        createdMap[node->label]=newFirstNode;
        
        while(!qe.empty()){
            UndirectedGraphNode * qe_top = qe.front(); qe.pop();
            UndirectedGraphNode * qe_copy_top = qe_copy.front();qe_copy.pop();
            //创建邻接节点
            int neighborsSize = qe_top->neighbors.size();
            for(int i=0; i<neighborsSize; i++){
                node = qe_top->neighbors[i];
                //判断当前节点是否已经创建过
                if(createdMap[node->label]!=NULL){
                    //如果已经创建了，直接从createdmap中取即可
                    qe_copy_top->neighbors.push_back(createdMap[node->label]);
                }
                else{
                    //如果还没创建，则创建新节点
                    //注意本题使用(UndirectedGraphNode*)malloc(sizeof(UndirectedGraphNode))会RUNTIME ERROR
                    UndirectedGraphNode * node_copy = new UndirectedGraphNode(node->label);
                    qe.push(node);
                    qe_copy.push(node_copy);
                    createdMap[node->label]=node_copy;
                    //添加到qe_copy_top的邻接节点
                    qe_copy_top->neighbors.push_back(node_copy);
                }
            }
        }
        return newFirstNode;
    }
};