[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

#

.

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
/ \
\_/

BFS，用hash来存储新的图和旧图的一一对应关系的点，采用BFS搜索。然后对每一个点存相邻点。

/**
* Definition for undirected graph.
* struct UndirectedGraphNode {
*     int label;
*     vector<UndirectedGraphNode *> neighbors;
*     UndirectedGraphNode(int x) : label(x) {};
* };
*/
class Solution {
public:
UndirectedGraphNode *cloneGraph(UndirectedGraphNode *node) {
unordered_map<UndirectedGraphNode * ,UndirectedGraphNode *> NodeMap;
//和克隆图之间的Map这样可以一次遍历完
queue<UndirectedGraphNode *> Qq;
if(node == NULL)
return node;
Qq.push(node);
while(!Qq.empty()){
UndirectedGraphNode *top = Qq.front();
Qq.pop();
if(NodeMap.count(top)==0){//没有节点
UndirectedGraphNode * Temp = new UndirectedGraphNode(top->label);
NodeMap[top] = Temp;
}
//保存相邻节点
for(auto it = top->neighbors.begin(); it!=top->neighbors.end(); ++it){
UndirectedGraphNode *adj = *it;
if(NodeMap.count(adj)==0){//没有该节点，创建节点，同时间也避免了环，之前遍历过的节点不会再遍历
UndirectedGraphNode *Temp = new UndirectedGraphNode(adj->label);
NodeMap[adj] = Temp;
Qq.push(adj);
}
NodeMap[top]->neighbors.push_back(NodeMap[adj]); //给定字节点所有链接节点，如果有环也会保留，因为没有入队列
}
}
return NodeMap[node];
}
};