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stronglyConnectedComponents.cpp
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stronglyConnectedComponents.cpp
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#include <iostream>
#include<stack>
#include<unordered_set>
#include<vector>
using namespace std;
void dfs(vector<int>* edges,int start,unordered_set<int> &visited,stack<int>&finished)
{
visited.insert(start);
for(int i=0;i<edges[start].size();i++)
{
if(visited.count(edges[start][i])==0)
{
dfs(edges,edges[start][i],visited,finished);
}
}
finished.push(start);
}
void dfs2(vector<int>* edgesT,int start,unordered_set<int> &visited,unordered_set<int>*component)
{
visited.insert(start);
component->insert(start);
for(int i=0;i<edgesT[start].size();i++)
{
if(visited.count(edgesT[start][i])==0)
{
dfs2(edgesT,edgesT[start][i],visited,component);
}
}
}
unordered_set<unordered_set<int>*>* SCC(vector<int>* edges,vector<int> edgesT[],int n)
{
unordered_set<int> visited;
stack<int>finished;
for(int i=0;i<n;i++)
{
if(visited.count(i)==0)
{
dfs(edges,i,visited,finished);
}
}
visited.clear();
unordered_set<unordered_set<int>*>* output=new unordered_set<unordered_set<int>*>();
while(finished.size()!=0)
{
int element=finished.top();
finished.pop();
if(visited.count(element)==0)
{
unordered_set<int>*component=new unordered_set<int>();
dfs2(edgesT,element,visited,component);
output->insert(component);
}
}
return output;
}
int main()
{
int v;
cin>>v;
int e;
cin>>e;
vector<int>*edges=new vector<int>[v];
vector<int>*edgesT=new vector<int>[v];
for(int i=0;i<e;i++)
{
int a,b;
cin>>a>>b;
edges[a-1].push_back(b-1);
edgesT[b-1].push_back(a-1);
}
unordered_set<unordered_set<int>*>* components=SCC(edges,edgesT,v);
unordered_set<unordered_set<int>*>::iterator it=components->begin();
while(it!=components->end())
{
unordered_set<int>* component=*it;
unordered_set<int>::iterator it2=component->begin();
while(it2!=component->end())
{
cout<<*it2+1<<" ";
it2++;
}
cout<<endl;
it++;
}
return 0;
}