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
/ \
\_/
DFS is OK, TAKE NOTICE the position of
exist.insert(make_pair(node, nodecpy)); The following is the AC code:
/**
* Definition for undirected graph.
* struct UndirectedGraphNode {
* int label;
* vector neighbors;
* UndirectedGraphNode(int x) : label(x) {};
* };
*/
class Solution {
public:
UndirectedGraphNode *DFS(UndirectedGraphNode *node, unordered_map& exist) {
if (exist.find(node) != exist.end())
return exist[node];
else {
UndirectedGraphNode *nodecpy = new UndirectedGraphNode(node->label);
exist.insert(make_pair(node, nodecpy));
UndirectedGraphNode *neighbor = NULL;
for (int i = 0; i < (node->neighbors).size(); ++i) {
neighbor = DFS((node->neighbors)[i], exist);
(nodecpy->neighbors).push_back(neighbor);
}
return nodecpy;
}
}
UndirectedGraphNode *cloneGraph(UndirectedGraphNode *node) {
unordered_map exist;
if (node == NULL)
return node;
return DFS(node,exist);
}
};