Find the Weak Connected Component in the Directed Graph
Find the number Weak Connected Component in the directed graph. Each node in the graph contains a label and a list of its neighbors. (a connected set of a directed graph is a subgraph in which any two vertices are connected by direct edge path.)
Example
Given graph:
A----->B C
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v v
->D E <- F
Return {A,B,D}, {C,E,F}. Since there are two connected component which are{A,B,D} and {C,E,F}
Note
Sort the element in the set in increasing order
Union-Find，并查集！注意fa每次都要重新求，因为fa的值可能在之前的循环中被更新。
1 /** 2 * Definition for Directed graph. 3 * struct DirectedGraphNode { 4 * int label; 5 * vector<DirectedGraphNode *> neighbors; 6 * DirectedGraphNode(int x) : label(x) {}; 7 * }; 8 */ 9 class Solution { 10 public: 11 /** 12 * @param nodes a array of directed graph node 13 * @return a connected set of a directed graph 14 */ 15 int find(unordered_map<int, int> &father, int x) { 16 if (father.find(x) == father.end()) { 17 father[x] = x; 18 return x; 19 } 20 while (x != father[x]) x = father[x]; 21 return x; 22 } 23 vector<vector<int>> connectedSet2(vector<DirectedGraphNode*>& nodes) { 24 // Write your code here 25 unordered_map<int, int> father; 26 int fa, fb, fn; 27 for (auto &n : nodes) { 28 for (auto &nn : n->neighbors) { 29 fa = find(father, n->label); 30 fb = find(father, nn->label); 31 if (fa != fb) { 32 if (fa > fb) father[fa] = fb; 33 else father[fb] = fa; 34 } 35 } 36 } 37 unordered_map<int, vector<int>> comp; 38 for (auto &n : nodes) { 39 fn = find(father, n->label); 40 comp[fn].push_back(n->label); 41 } 42 vector<vector<int>> res; 43 for (auto &c : comp) { 44 sort(c.second.begin(), c.second.end()); 45 res.push_back(c.second); 46 } 47 return res; 48 } 49 };