LeetCode133：Clone Graph
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 node0to both nodes1and2. - Second node is labeled as
1. Connect node1to node2. - Third node is labeled as
2. Connect node2to node2(itself), thus forming a self-cycle.
Visually, the graph looks like the following:
1
/ \
/ \
0 --- 2
/ \
\_/
解题思路：
本题要解决的问题就是对一个图进行clone，这不禁让我们想起图的遍历：DFS和BFS，所以我们可以再遍历图中某个点时，增加一些附加的操作而不仅仅是访问它，这里我们要增加的附加操作即对该点进行clone。
现在我们利用DFS和BFS两种方式进行解题。
实现代码：
#include <iostream> #include <vector> #include <queue> #include <unordered_map> using namespace std; /* 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 / \ \_/ */ struct UndirectedGraphNode { int label; vector<UndirectedGraphNode *> neighbors; UndirectedGraphNode(int x) : label(x) {}; }; class Solution { public: UndirectedGraphNode *cloneGraph(UndirectedGraphNode *node) { if(node == NULL) return NULL; unordered_map<int, UndirectedGraphNode*> hashtable;//标志位，是否已拷贝了key为label，value为新拷贝的node return dfsclone(node, hashtable); } //DFS UndirectedGraphNode *dfsclone(UndirectedGraphNode *node, unordered_map<int, UndirectedGraphNode*> &hashtable) { if(node == NULL) return NULL; if(hashtable.count(node->label) > 0) return hashtable[node->label];//已经拷贝好了，则直接返回即可，否则进行下面的拷贝操作 UndirectedGraphNode *copyNode = new UndirectedGraphNode(node->label); hashtable[copyNode->label] = copyNode; vector<UndirectedGraphNode *>::iterator iter; for(iter = node->neighbors.begin(); iter != node->neighbors.end(); ++iter) { copyNode->neighbors.push_back(dfsclone(*iter, hashtable));//进行深度优先算法拷贝 } return copyNode; } //BFS UndirectedGraphNode *bfsclone(UndirectedGraphNode *node, unordered_map<int, UndirectedGraphNode*> &hashtable) { if(node == NULL) return NULL; queue<UndirectedGraphNode *> qu; UndirectedGraphNode *copyNode = new UndirectedGraphNode(node->label); hashtable[copyNode->label] = copyNode; qu.push(node); while(!qu.empty()) { UndirectedGraphNode *tnode = qu.front(); qu.pop(); vector<UndirectedGraphNode *>::iterator iter; for(iter = node->neighbors.begin(); iter != node->neighbors.end(); ++iter) { if(hashtable.count((*iter)->label) == 0) { UndirectedGraphNode *tnode = new UndirectedGraphNode((*iter)->label); hashtable[(*iter)->label] = tnode; qu.push(*iter); } (hashtable[tnode->label])->neighbors.push_back(hashtable[(*iter)->label]); } } return copyNode; } }; int main(void) { return 0; }