Find the Connected Component in the Undirected Graph
Find the number connected component in the undirected graph. Each node in the graph contains a label and a list of its neighbors. (a connected component (or just component) of an undirected graph is a subgraph in which any two vertices are connected to each other by paths, and which is connected to no additional vertices in the supergraph.)
Example
Given graph:
A------B C
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D E
Return {A,B,D}, {C,E}. Since there are two connected component which is {A,B,D}, {C,E}
DFS:
1 /** 2 * Definition for Undirected graph. 3 * struct UndirectedGraphNode { 4 * int label; 5 * vector<UndirectedGraphNode *> neighbors; 6 * UndirectedGraphNode(int x) : label(x) {}; 7 * }; 8 */ 9 class Solution { 10 public: 11 /** 12 * @param nodes a array of Undirected graph node 13 * @return a connected set of a Undirected graph 14 */ 15 void dfs(vector<UndirectedGraphNode*> &nodes, vector<int> &path, 16 unordered_set<UndirectedGraphNode*> &visit, UndirectedGraphNode* n) { 17 visit.insert(n); 18 path.push_back(n->label); 19 for (auto &nn : n->neighbors) if (visit.find(nn) == visit.end()) { 20 dfs(nodes, path, visit, nn); 21 } 22 } 23 vector<vector<int>> connectedSet(vector<UndirectedGraphNode*>& nodes) { 24 // Write your code here 25 unordered_set<UndirectedGraphNode*> visit; 26 vector<vector<int>> res; 27 vector<int> path; 28 for (auto &n : nodes) { 29 if (visit.find(n) == visit.end()) { 30 path.clear(); 31 dfs(nodes, path, visit, n); 32 sort(path.begin(), path.end()); 33 res.push_back(path); 34 } 35 } 36 return res; 37 } 38 };
BFS:
1 /** 2 * Definition for Undirected graph. 3 * struct UndirectedGraphNode { 4 * int label; 5 * vector<UndirectedGraphNode *> neighbors; 6 * UndirectedGraphNode(int x) : label(x) {}; 7 * }; 8 */ 9 class Solution { 10 public: 11 /** 12 * @param nodes a array of Undirected graph node 13 * @return a connected set of a Undirected graph 14 */ 15 vector<vector<int>> connectedSet(vector<UndirectedGraphNode*>& nodes) { 16 // Write your code here 17 unordered_set<UndirectedGraphNode*> visit; 18 vector<vector<int>> res; 19 vector<int> path; 20 queue<UndirectedGraphNode*> que; 21 for (auto &n : nodes) { 22 if (visit.find(n) == visit.end()) { 23 path.clear(); 24 visit.insert(n); 25 for (que.push(n); !que.empty(); que.pop()) { 26 auto u = que.front(); 27 path.push_back(u->label); 28 for (auto nn : u->neighbors) if (visit.find(nn) == visit.end()) { 29 visit.insert(nn); 30 que.push(nn); 31 } 32 } 33 sort(path.begin(), path.end()); 34 res.push_back(path); 35 } 36 } 37 return res; 38 } 39 };