Submission #260926

#	Time	Username	Problem	Language	Result	Execution time	Memory
260926		emanIaicepsa	Duathlon (APIO18_duathlon)	C++14	31 / 100	192 ms	24568 KiB

count_triplets

#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define pii pair<ll,ll>
#define vi vector<int>
#define pb emplace_back
#define fi first
#define se second
#define all(n) (n).begin(),(n).end()
#define mem(n,m) memset(n,m,sizeof(n))
#define IOS ios::sync_with_stdio(0), cin.tie(0)
#define dbg(...) cerr<<#__VA_ARGS__<<" = ";_do(__VA_ARGS__);
template<typename A> void _do(A x){cerr<<x<<'\n';}
template<typename A,typename ...B> void _do(A x,B ...y){cerr<<x<<", ";_do(y...);}

const int mxn = 100005;
ll C(ll x){
    return (x)*(x-1)*(x-2)/6*2;
}

ll P(ll x){
    return C(x)*3;
}

ll n,m;
vi E[mxn], E2[mxn];
ll siz[mxn], ans=0, l[mxn], d[mxn], bcc[mxn], bcc_siz[mxn], dfn, bccid, vis[mxn], rt[mxn];
stack<int> s;

void dfs(int x,int p){
    l[x] = d[x] = ++dfn;
    s.push(x);
    for(auto i:E[x]){
        if(i==p) continue;
        if(!d[i]){
            dfs(i,x);
            l[x] = min(l[x],l[i]);
        }
        else{
            l[x] = min(l[x],d[i]);
        }
    }
    if(l[x] == d[x]){
        bccid++;
        for(int i;i!=x;){
            i = s.top(); s.pop();
            bcc[i] = bccid;
        }
    }
}

void bcc_dfs(int x,int p,int anc){
    rt[x] = anc;
    siz[x] = bcc_siz[x];
    vis[x] = 1;
    for(auto i:E2[x]){
        if(i==p) continue;
        bcc_dfs(i,x,anc);
        siz[x] += siz[i];
    }
}

void bcc_dfs2(int x,int p,int anc){
    vis[x] = 1;
    for(auto i:E2[x]){
        if(i==p) continue;
        bcc_dfs2(i,x,anc);
        ans += siz[i] * (siz[anc] - siz[i] - bcc_siz[x]) * bcc_siz[x];
    }
    ans += (siz[x]-bcc_siz[x]) * (siz[anc]-siz[x]);
}

signed main(){
	IOS;
    cin>>n>>m;
    for(int i=1,a,b;i<=m;i++){
        cin>>a>>b;
        E[a].pb(b);
        E[b].pb(a);
    }


    for(int i=1;i<=n;i++) if(!d[i]) dfs(i,0);

    for(int i=1;i<=n;i++){
        //dbg(i, bcc[i]);
        bcc_siz[bcc[i]]++;
        for(auto j:E[i]){
            if(bcc[i] == bcc[j]) continue;
            E2[bcc[i]].pb(bcc[j]);
            E2[bcc[j]].pb(bcc[i]);
        }
    }

    for(int i=1;i<=bccid;i++){
        sort(all(E2[i]));
        E2[i].resize(unique(all(E2[i]))-E2[i].begin());
    }

    for(int i=1;i<=bccid;i++){
        if(!vis[i]){
            bcc_dfs(i,0,i);
        }
    }
//    for(int i=1;i<=bccid;i++){
//        dbg(i, siz[i]);
//    }
    mem(vis,0);
    for(int i=1;i<=bccid;i++){
        if(bcc_siz[i]>=3){
            ll x = bcc_siz[i];
            ans += P(x);
            ans += (x-1) * (x-1) * (siz[rt[i]] - x) * 2;
        }
        if(!vis[i]){
            bcc_dfs2(i,0,i);
        }
    }

    cout<<ans<<'\n';

}
/*
3 3
1 2
2 3
3 1

4 4
1 2
2 3
3 4
2 4

5 4
1 2
2 3
1 3
4 5
*/

• Subtask 1: 0 / 5
• Subtask 2: 0 / 11
• Subtask 3: 8 / 8
• Subtask 4: 10 / 10
• Subtask 5: 13 / 13
• Subtask 6: 0 / 15
• Subtask 7: 0 / 20
• Subtask 8: 0 / 8
• Subtask 9: 0 / 10