Submission #981456

#	Time	Username	Problem	Language	Result	Execution time	Memory
981456		shenfe1	Duathlon (APIO18_duathlon)	C++17	8 / 100	125 ms	29784 KiB

count_triplets

#include <bits/stdc++.h>
 
#pragma optimize("Ofast")
#pragma target("avx2")
 
using namespace std;
 
#define ll long long
#define ld long double
#define pb push_back
#define pf push_front
#define pii pair<int,int>
#define all(v) v.begin(),v.end()
#define F first
#define S second
#define mem(a,i) memset(a,i,sizeof(a))
#define sz(s) (int)s.size()
#define y1 yy
#define ppb pop_back
#define lb lower_bound
#define ub upper_bound
#define gcd(a,b) __gcd(a,b)
#define in insert
#define int ll

const int MAX=1e5+15;
const int B=300;
const int N=104;
const int block=400;
const int maxB=MAX/B+10;
const ll inf=2e18;  
const int mod=998244353;
const int mod1=1e9+9;
const ld eps=1e-9;
 
int dx[8]={1,0,-1,0,1,-1,-1,1};
int dy[8]={0,1,0,-1,1,-1,1,-1};
 
int binpow(int a,int n){
  if(!n)return 1;
  if(n%2==1)return a*binpow(a,n-1)%mod;
  int k=binpow(a,n/2);
  return k*k%mod;
}

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

int n,m;
vector<int> g[MAX];
int use[MAX];
int tin[MAX],fup[MAX],timer;
map<pii,int> br;
int cnt=0;
bool was;

void dfs(int v,int p=-1){
  tin[v]=fup[v]=++timer;
  use[v]=1;
  cnt++;
  for(auto to:g[v]){
    if(to==p)continue;
    if(!use[to]){
      dfs(to,v);
      fup[v]=min(fup[v],fup[to]);
      if(fup[to]>tin[v]){
        was=1;
        br[{v,to}]=br[{to,v}]=1;
      }
    }
    else{
      fup[v]=min(fup[v],tin[to]);
    }
  }
}

struct DSU{
  int f[MAX];

  void init(int n){
    for(int i=1;i<=n;i++){
      f[i]=i;
    }
  }

  int get(int v){
    if(f[v]==v)return v;
    return f[v]=get(f[v]);
  }

  void unite(int a,int b){
    a=get(a);
    b=get(b);
    if(rng()%2)swap(a,b);
    f[a]=b;
  }
}D;

int s[MAX];
int S[MAX];
int pr[MAX];
int PR[MAX];
vector<int> g1[MAX];

void dfs1(int v,int st,int p=-1){
  pr[v]=p;
  PR[v]=st;
  use[v]=1;
  sort(all(g1[v]));
  g1[v].erase(unique(all(g1[v])),g1[v].end());
  S[v]=s[v];
  for(auto to:g1[v]){
    if(to==p)continue;
    dfs1(to,st,v);
    S[v]+=S[to];
  }
}

void solve(){
  cin>>n>>m;
  for(int i=1;i<=m;i++){
    int a,b;
    cin>>a>>b;
    g[a].pb(b);
    g[b].pb(a);
  }
  int ans=0;
  for(int i=1;i<=n;i++){
    if(!use[i]){
      dfs(i);
      if(was)ans+=cnt*(cnt-1)*(cnt-2)/3;
      else ans+=cnt*(cnt-1)*(cnt-2);
      cnt=0;
      was=0;
    }
  }
  cout<<ans<<"\n";
  return;
  D.init(n);
  for(int i=1;i<=n;i++){
    for(auto to:g[i]){
      if(!br.count({i,to})){
        D.unite(i,to);
      }
    }
  }
  for(int i=1;i<=n;i++){
    s[D.get(i)]++;
    for(auto to:g[i]){
      if(D.get(i)!=D.get(to)){
        g1[D.get(i)].pb(D.get(to));
      }
    }
  }
  // cerr<<"Ok\n";
  mem(use,0);
  for(int i=1;i<=n;i++){
    if(!use[D.get(i)]){
      dfs1(D.get(i),D.get(i));
    }
  }
  for(int i=1;i<=n;i++){
    if(D.get(i)==i){
      ans+=s[i]*(s[i]-1)*(s[i]-2)/6;
      int up=S[PR[i]]-S[i];
      int down=S[i]-s[i];
      ans+=s[i]*up*down;
      ans+=s[i]*(s[i]-1)*(S[PR[i]]-s[i]);
      for(auto to:g1[i]){
        if(to==pr[i])continue;
        ans+=S[to]*s[i]*(S[i]-S[to]-s[i]);
      }
    }
  }
  cout<<ans*2<<"\n";
}
 
signed main(){
  //  freopen("help.in","r",stdin);
  //  freopen("help.out","w",stdout);
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  // prec();
  int t=1;
  // cin>>t;
  while(t--)solve();
}

Compilation message (stderr)

count_triplets.cpp:3: warning: ignoring '#pragma optimize ' [-Wunknown-pragmas]
    3 | #pragma optimize("Ofast")
      | 
count_triplets.cpp:4: warning: ignoring '#pragma target ' [-Wunknown-pragmas]
    4 | #pragma target("avx2")
      |

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