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

#

.

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
/ \
\_/

【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;
}
};