LeetCode: Clone Graph [133]

標籤：leetcode   演算法   面試   

【題目】

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         /          \_/

【題意】

    複製無向圖。無向圖中每個點有一個值唯一的label和鄰接節點的label集合

【思路】

    DFS或者BFS遍曆無向圖完成賦值
    【注意】本題中使用malloc建立節點會報RUNTIME ERROR錯誤，必須用new建立節點

    

【代碼】

/** * 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;      //已經複製的節點                //建立第一個節點        //注意本題使用(UndirectedGraphNode*)malloc(sizeof(UndirectedGraphNode))會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();            //建立鄰接節點            int neighborsSize = qe_top->neighbors.size();            for(int i=0; i<neighborsSize; i++){                node = qe_top->neighbors[i];                //判斷當前節點是否已經建立過                if(createdMap[node->label]!=NULL){                    //如果已經建立了，直接從createdmap中取即可                    qe_copy_top->neighbors.push_back(createdMap[node->label]);                }                else{                    //如果還沒建立，則建立新節點                    //注意本題使用(UndirectedGraphNode*)malloc(sizeof(UndirectedGraphNode))會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的鄰接節點                    qe_copy_top->neighbors.push_back(node_copy);                }            }        }        return newFirstNode;    }};