Submission #738617

#	Time	Username	Problem	Language	Result	Execution time	Memory
738617		089487	Duathlon (APIO18_duathlon)	C++14	0 / 100	134 ms	40788 KiB

count_triplets

#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx,popcnt,sse4,abm")
#include<bits/stdc++.h>
#define int long long
#define quick ios::sync_with_stdio(0);cin.tie(0);
#define rep(x,a,b) for(int x=a;x<=b;x++)
#define repd(x,a,b) for(int x=a;x>=b;x--)
#define lowbit(x) (x&-x)
#define sz(x) (int)(x.size())
#define F first
#define S second
#define all(x) x.begin(),x.end()
#define mp make_pair
#define eb emplace_back
using namespace std;
typedef pair<int,int> pii;
void debug(){
    cout<<"\n";
}
template <class T,class ... U >
void debug(T a, U ... b){
    cout<<a<<" ",debug(b...);
}
const int N=2e5+7;
const int INF=1e18;
vector<int> v[N];
vector<int> v2[N];
vector<int> v3[N];
int in[N];
int low[N];
int t=1;
int num;
int sz[N];
bool cut[N];
stack<int> st;
void add_edge(int a,int b){
	v2[a].eb(b);
	v2[b].eb(a);
	//debug(a,"<->",b);
}
void dfs(int x,int p=-1){
	in[x]=low[x]=t++;
	st.push(x);
	bool ct=false;
	for(int i:v[x]){
		if(i==p) continue;
		if(in[i]) low[x]=min(low[x],in[i]);
		else{
			dfs(i,x);
			if(in[x]<=low[i]) ct=true;
			low[x]=min(low[x],low[i]);
		}
	}
	if(p==-1){
		ct=(sz(v[x])>=2);
	}
	if(p==-1||in[p]<=low[x]){
		++num;
		while(sz(st)){
			int x2=st.top();
			st.pop();
			add_edge(num,x2);
			if(x2==x) break;
		}
		if(p!=-1)add_edge(num,p);
		cut[num]=ct;
	}
}
pii e[N];
int sum;
int n;
int Sz[N];
int Sz2[N];
bool vis[N];
int fa[N];
void dfs_sz(int x,int p=-1){
	Sz[x]=sz[x];
	for(int i:v2[x]){
		if(i!=p){
			dfs_sz(i,x);
			Sz[x]+=Sz[i];
		}
	}
	sum=Sz[x];
}
int C2(int x){
	if(x<2) return 0;
	return x*(x-1);
}
int C3(int x){
	if(x<3) return 0;
	return x*(x-1)*(x-2);
}
int ans=0;
void solve(int x,int p=-1){
	fa[x]=p;
	vis[x]=true;
	for(int i:v2[x]){
		if(!vis[i]) solve(i,x);
	}
	if(x<=n){
		int a=sum-Sz[x];
		int b=Sz[x]-1;
	//	debug("solve",x,Sz[x],a,b);
		
		ans+=a*b*2;
		int s=0;
		for(int i:v2[x]){
			if(fa[i]==x) ans+=C2(sz(v2[i])-1);
		}
	}
	else{
		for(int i:v2[x]){
			if(fa[i]!=x){//Up
				int Lft=sum-Sz[x];
	//			debug(x,"Add",i,"i",Lft,Lft*C2(sz(v2[x])-1)*2);
				ans+=Lft*C2(sz(v2[x])-1)*2;
			}
			else{
				int Lft=Sz[i]-1;
	//			debug(x,"Add",i,"i",Lft,Lft*C2(sz(v2[x])-1)*2);
				ans+=Lft*C2(sz(v2[x])-1)*2;
			}
		}
	}
}
signed main(){
	quick
	int m;
	cin>>n>>m;
	rep(i,1,m){
		cin>>e[i].F>>e[i].S;
		v[e[i].F].eb(e[i].S);
		v[e[i].S].eb(e[i].F);
	}
	num=n;
	dfs(1);
	rep(i,1,n) sz[i]=1;
	ans=0;
	rep(i,1,num){
		if(!vis[i]){
			dfs_sz(i);
			solve(i);
			break;
		}
	}
	//rep(i,1,n) cout<<Sz[i]<<" \n"[i==n];
	cout<<ans<<"\n";
	return 0;
}

Compilation message (stderr)

count_triplets.cpp: In function 'void solve(long long int, long long int)':
count_triplets.cpp:107:7: warning: unused variable 's' [-Wunused-variable]
  107 |   int s=0;
      |       ^

• Subtask 1: 0 / 5
• Subtask 2: 0 / 11
• Subtask 3: 0 / 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