Submission #260882

#	Time	Username	Problem	Language	Result	Execution time	Memory
260882		emanIaicepsa	Duathlon (APIO18_duathlon)	C++14	31 / 100	173 ms	24824 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...);}

ll n,m;
vi E[100005];
ll siz[100005], ans=0;
bool vis[100005];

int pa[100005][18], dep[100005];

ll C(ll x){
    return (x)*(x-1)*(x-2)/6*2;
}

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

vector<pii> circ;

void dfs(int x,int p){
    vis[x] = 1;
    siz[x] = 1;
    dep[x] = dep[p] + 1;
    pa[x][0] = p;
    for(int i=1;i<=__lg(n);i++){
        pa[x][i] = pa[ pa[x][i-1] ][i-1];
    }
    for(auto i:E[x]){
        if(i==p) continue;
        else if(vis[i]){
            if(x<i)circ.pb(x,i);
        }
        else{
            dfs(i,x);
            siz[x] += siz[i];
        }
    }
}

void dfs2(int x,int p,int anc){
    vis[x] = 1;
    for(auto i:E[x]){
        if(vis[i]) continue;
        dfs2(i,x,anc);
        ans += siz[i] * (siz[anc]-siz[i]-1);
    }
    ans += (siz[x]-1) * (siz[anc]-siz[x]);
}

int dis(int x,int y){
    ll ans = 0;
    if(dep[x]<dep[y]) swap(x,y);
    for(int i=__lg(n),le=dep[x]-dep[y];i>=0;i--){
        if(le>=(1<<i)){
            le -= 1<<i;
            ans += 1<<i;
            x = pa[x][i];
        }
    }
    if(x==y) return ans;
    for(int i=__lg(n);i>=0;i--){
        if(pa[x][i] != pa[y][i]){
            x = pa[x][i];
            y = pa[y][i];
            ans += (1<<i)*2;
        }
    }
    return ans+2;
}

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(!vis[i]) dfs(i,0);
    mem(vis,0);
    for(int i=1;i<=n;i++) if(!vis[i]) dfs2(i,0,i);

    for(auto i:circ){
        int d = dis(i.fi,i.se) + 1;
        ans -= C(d);
        ans += P(d);
    }

    cout<<ans<<'\n';

}
/*
3 3
1 2
2 3
3 1
*/

• 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