LeetCode 133. 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
/ \
\_/

When comes to graph, usually comes with a mess. Actually graph is not that complicated.

This problem is a good one to dissolve the fear.

// this is to use BFS.
UndirectedGraphNode *cloneGraph(UndirectedGraphNode *node) {
if(!node) return NULL;
unordered_map<UndirectedGraphNode*, UndirectedGraphNode*> hashMap;
hashMap.insert({node, new UndirectedGraphNode(node->label)});
queue<UndirectedGraphNode*> nodes;
nodes.push(node);
while(!nodes.empty()) {
auto v = nodes.front();
nodes.pop();
for(UndirectedGraphNode* e : v->neighbors) {
if(hashMap.find(e) == hashMap.end()) {
hashMap.insert({e,  new UndirectedGraphNode(e->label)});
nodes.push(e);
}
(hashMap[v]->neighbors).push_back(hashMap[e]);
}
}
return hashMap[node];
}