[Lintcode] 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 with which any of the vertices is connected by direct edge path.)

Example

Given Graph:

A----->B  C \     |  |   \    |  |   \   |  |    \  v  v     ->D  E <- F

Return {A,B,D}, {C,E,F} . Since there is and connected component which is{A,B,D} and {C,E,F}

Note

Sort the element in the set in increasing order.

Solution:

and check the set. Iterate through each change and update the collection where each node resides.

/** Definition for Directed graph. * struct DIRECTEDGRAPHNODE {* int label; * Vector<directedgraphnode *&G T Neighbors; * Directedgraphnode (int x): label (x) {}; * }; */classSolution {//Use union-set to solvePrivate:    intFind (unordered_map<int,int> &nodemap,intlabel) {        if(nodemap.find (label) = =Nodemap.end ()) {Nodemap[label]=label; returnlabel; //If this node doesn ' t belong to any union-set, create a new set}Else{            //This node belongs to some set, find the root of the set            intres =Nodemap[label];  while(Nodemap[res]! =Res) Res=Nodemap[res]; returnRes; }    } Public:    /** * @param nodes A array of directed graph node * @return A connected set of a directed graph*/Vector<vector<int>> ConnectedSet2 (vector<directedgraphnode*>&nodes) {Unordered_map<int,int>Nodemap; Vector<vector<int> >result;  for(inti =0; i < nodes.size (); + +i) {             for(intj =0; J < (nodes[i]->neighbors). Size (); + +j) {                intS1 = Find (Nodemap, nodes[i]->label); intS2 = Find (Nodemap, (nodes[i]->neighbors) [j]->label); if(S1! =S2) {                    //Union sets                    if(S1 < s2) NODEMAP[S2] =S1; ElseNODEMAP[S1] =S2; }Else{                    // do nothing} }} unordered_map<int,int>Setid2vecid;  for(inti =0; i < nodes.size (); + +i) {            intLabel = nodes[i]->label; intSetId =Find (nodemap, label); if(Setid2vecid.find (setId) = =Setid2vecid.end ()) {Vector<int>VEC; Setid2vecid[setid]=result.size ();            Result.push_back (VEC); }            intIDX =Setid2vecid[setid];        Result[idx].push_back (label); }         for(inti =0; i < result.size (); + +i) sort (Result[i].begin (), Result[i].end ()); returnresult; }};

Inspired by:http://www.cnblogs.com/easonliu/p/4607300.html

[Lintcode] Find the Weak Connected Component in the Directed Graph