[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
/ \
\_/

思路：用map存储创建的新的结点，其中key是结点的label值，value是结点的指针值。

/**
* 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;
UndirectedGraphNode *pnode = node;
UndirectedGraphNode *head = new UndirectedGraphNode(node->label);
UndirectedGraphNode *p = head;
map<int,UndirectedGraphNode *> labelAndNode;
labelAndNode[head->label] = head;
pNodeNeighbors(pnode,p,labelAndNode);
return head;
}
private:
void pNodeNeighbors(UndirectedGraphNode *&pnode,UndirectedGraphNode *&p,map<int,UndirectedGraphNode *> &labelAndNode)
{
int num = pnode->neighbors.size();
UndirectedGraphNode *pnew ;
for(int i = 0;i<num;i++)
{
if(labelAndNode.count(pnode->neighbors[i]->label)==0)
{
pnew = new UndirectedGraphNode(pnode->neighbors[i]->label);
labelAndNode[pnode->neighbors[i]->label] = pnew;
p->neighbors.push_back(pnew);
pNodeNeighbors(pnode->neighbors[i],p->neighbors[i],labelAndNode);
}
else
{
pnew =  labelAndNode[pnode->neighbors[i]->label];
p->neighbors.push_back(pnew);
}

}

}
};