Submission #979315

#	Time	Username	Problem	Language	Result	Execution time	Memory
979315		imarn	Duathlon (APIO18_duathlon)	C++14	100 / 100	77 ms	36044 KiB

count_triplets

#include<bits/stdc++.h>
#define f first
#define s second
#define ll long long
#define pb push_back
#define pii pair<int,int>
#define pll pair<ll,ll>
#define sz(x) (int)x.size()
#define all(x) x.begin(),x.end()
#define vi vector<int>
#define vvi vector<vi>
using namespace std;
const int N=1e5+5;
vi g[N];stack<int>st;
bool vis[3*N]{0};
vector<int>bst[500001];ll x=0,n;
ll d[N]{0},lo[N]{0},t=0,ap[N]{0},id[N]{0},cur=1,isap[N]{0},sz[N];
void dfs(int u,int p){x++;
    lo[u]=d[u]=++t;st.push(u);
    for(auto v:g[u]){
        if(!d[v]){
            dfs(v,u);
            lo[u]=min(lo[u],lo[v]);
            if(d[u]<=lo[v]){
                bst[u].pb(cur+n);bst[cur+n].pb(u);
                while(bst[cur+n].empty()||bst[cur+n].back()!=v){
                    bst[cur+n].pb(st.top());bst[st.top()].pb(cur+n);st.pop();
                }cur++;
            }
        }
        else if(v!=p)lo[u]=min(lo[u],d[v]);
    }
}
ll ans=0;
void solve(int u){
    sz[u]=(u<=n);vis[u]=1;
    for(auto v:bst[u]){
        if(vis[v])continue;
        solve(v);sz[u]+=sz[v];
        if(u>n)ans-=sz[v]*(sz[v]-1)*(sz(bst[u])-1);
    }
    if(u>n)ans-=(x-sz[u])*(x-sz[u]-1)*(sz(bst[u])-1);
}
int main(){
    ios_base::sync_with_stdio(0);cin.tie(0);
    int m;cin>>n>>m;
    for(int i=1;i<=m;i++){
        int u,v;cin>>u>>v;
        g[u].pb(v);g[v].pb(u);
    }
    for(int i=1;i<=n;i++){
        if(d[i])continue;
        dfs(i,i);solve(i);
        ans+=(x)*(x-1)*(x-2);x=0,t=0;
    }cout<<ans;
}

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