LeetCode: Clone Graph

LeetCode: 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
         / 
         \_/

地址：https://oj.leetcode.com/problems/clone-graph/
算法：把整个图复制下来，基本就是利用map来完成的，复制的过程采用递归完成。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){
            return NULL;
        }
        map<int,UndirectedGraphNode *> hash_table;
        set<int> isTraved;
        return subClone(node,hash_table,isTraved);
    }
    UndirectedGraphNode *subClone(UndirectedGraphNode *node, map<int,UndirectedGraphNode*> &hash_table, set<int> &isTraved){
        if(!node){
            return NULL;
        }
        int label = node->label;
        if(isTraved.find(label) != isTraved.end()){
            return hash_table[label];
        }
        if(hash_table.find(label) == hash_table.end()){
            hash_table[label] = new UndirectedGraphNode(label);
        }
        isTraved.insert(label);
        UndirectedGraphNode *p = hash_table[label];
        vector<UndirectedGraphNode *>::iterator it = node->neighbors.begin();
        for(; it != node->neighbors.end(); ++it){
            p->neighbors.push_back(subClone(*it,hash_table,isTraved));
        }
        return p;
    }
};