Strongly Connected Component_KosarajuAlgo

//In the Name of Allah Most Gracious, Most Merciful//
/*If you want something you've never had, you have  to do something you never did.*/

#include<bits/stdc++.h>
using namespace std;


#define pb push_back
#define ll unsigned long long
#define pii pair<int,int>
#define pll pair<ll,ll>
#define M 1000007
#define INFL 1e18
#define PI acos(-1)
#define mp make_pair
#define fast_in_out ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
//const int fx[]= {+1,-1,+0,+0};
//const int fy[]= {+0,+0,+1,-1};
//const int fx[]={+0,+0,+1,-1,-1,+1,-1,+1};   // Kings Move
//const int fy[]={-1,+1,+0,+0,+1,+1,-1,-1};  // Kings Move
//const int fx[]={-2, -2, -1, -1,  1,  1,  2,  2};  // Knights Move
//const int fy[]={-1,  1, -2,  2, -2,  2, -1,  1}; // Knights Move
bool visited[M];
int finish_time[M];
vector<int>adj[M],revAdj[M];
vector<int>scc[M];
int cost[M];
vector<pii>v;
vector<int>vv;
int t=0;
int MOD=1e9+7;

void dfs1(int src)
{
    visited[src]=true;
    for(int i=0;i<adj[src].size();i++)
    {
        int k=adj[src][i];
        if(visited[k]==false)
        {
            dfs1(k);
        }
    }
    finish_time[src]=++t;
}

void dfs2(int src,int p)
{
    visited[src]=true;
   // cout<<src<<" "<<p<<endl;
    scc[p].pb(src);
    for(int i=0;i<revAdj[src].size();i++)
    {
        int k=revAdj[src][i];
        if(visited[k]==false)
        {
            dfs2(k,p);
        }
    }
}


int main()
{
    fast_in_out;
    //freopen("input.txt","r",stdin);
    //freopen("output.txt","w",stdout);
    int n;
    cin>>n;
    for(int i=1;i<=n;i++)
    {
        cin>>cost[i];
    }
    int m;
    cin>>m;
    for(int i=0;i<m;i++)
    {
        int x,y;
        cin>>x>>y;
        adj[x].pb(y);
        revAdj[y].pb(x);
    }
    memset(visited,false,sizeof visited);
    for(int i=1;i<=n;i++)
    {
        if(visited[i]==false)
        {
            dfs1(i);
        }
    }
    for(int i=1;i<=n;i++)
    {
        v.pb(mp(finish_time[i],i));
    }
    sort(v.begin(),v.end());
    int num=1;
    memset(visited,false,sizeof visited);
    ll sum=0;
    ll total=1;
    for(int i=v.size()-1;i>=0;i--)
    {
        int k=v[i].second;
        if(visited[k]==false)
        {
            dfs2(k,num);
            num++;
        }
    }
//    for(int i=1;i<num;i++)
//    {
//        for(int j=0;j<scc[i].size();j++)
//        {
//            cout<<i<<" "<<scc[i][j]<<endl;
//        }
//    }
    int total_scc=num-1;
    cout<<total_scc<<endl;

}