HackerEarth Connecting the special nodes problem solution

• No self-loop or multiple edges should be present 
• No connected components with more than one special node should be present
• Each node in the graph should belong to a component with exactly one special node

#include<bits/stdc++.h>
#define LL long long int
#define M 1000000007
#define reset(a) memset(a,0,sizeof(a))
#define rep(i,j,k) for(i=j;i<=k;++i)
#define per(i,j,k) for(i=j;i>=k;--i)
#define print(a,start,end) for(i=start;i<=end;++i) cout<<a[i];
#define endl "n"
#define eps 0.00000001
#define check(a , b , c) assert(a >= b && a <= c)
LL pow(LL a,LL b,LL m){LL x=1,y=a;while(b > 0){if(b%2 == 1){x=(x*y);if(x>m) x%=m;}y = (y*y);if(y>m) y%=m;b /= 2;}return x%m;}
LL gcd(LL a,LL b){if(b==0) return a; else return gcd(b,a%b);}
LL gen(LL start,LL end){LL diff = end-start;LL temp = rand()%start;return temp+diff;}
using namespace std;
int u[200001];
int v[200001];
int w[200001];
vector<int> graph[200001];
bool visit[200001];
int sz = 0;
int eg = 0;
int deg[200001];
vector<pair<int,int> > watered;
vector<pair<int,int> > dry;
void dfs(int node)
    {
        sz++;
        visit[node] = 1;
        eg += deg[node];
        for(int i: graph[node])
            {
                if(visit[i] == 0)
                    {
                        visit[i] = 1;
                        dfs(i);
                    }
            }
    }
int main()
    {
        ios_base::sync_with_stdio(0);
        int n , m , k;
        cin >> n >> m >> k;
        for(int i = 0; i < m; i++)
            {
                cin >> u[i] >> v[i];
                graph[u[i]].push_back(v[i]);
                graph[v[i]].push_back(u[i]);
                ++deg[u[i]];
                ++deg[v[i]];
            }
        for(int i = 0; i < k; i++)
            cin >> w[i];
        LL ans1 = 0 , ans2 = 0;
        LL maxsz = 0;
        for(int i = 0; i < k; i++)
            {
                sz = 0;
                eg = 0;
                if(visit[w[i]] == 1)
                    continue;
                dfs(w[i]);
                maxsz = max(maxsz , (LL)sz);
                eg /= 2;
                watered.push_back(make_pair(sz , eg));
                ans1 += (sz * (sz - 1)) / 2 - eg;
            }
        for(int i = 1; i <= n; i++)
            {
                if(visit[i] == 0)
                    {
                        sz = 0;
                        eg = 0;
                        dfs(i);
                        eg /= 2;
                        dry.push_back(make_pair(sz , eg));
                        ans1 += (sz * (sz - 1)) / 2 - eg;
                    }
            }
        sort(watered.begin() , watered.end());
    
        LL pre = 0 , cur = 0;
        for(int i = 0; i < dry.size(); i++)
            {
                ans2 = ans2 + pre * dry[i].first;
                ans1 += pre * dry[i].first;
                pre += dry[i].first;
            }
        
        ans2 += pre * maxsz;
        ans1 += pre * maxsz;
        cout << ans1 << " " << ans2;
                
    }