Submission #1127329

#	Time	Username	Problem	Language	Result	Execution time	Memory
1127329		czauderna	Duathlon (APIO18_duathlon)	C++20	100 / 100	86 ms	30148 KiB

count_triplets

// Solve dla całego zadnia
// O(n)
#include <bits/stdc++.h>
using namespace std;
#define pb push_back
typedef long long ll;
const int N = 2e5+3;
vector<int> grf[N], tree[N], stos;
ll siz[N], out, ile;
int n, pre[N], low[N], tmr, cnt=1;
void dfs(int v, int p){
    pre[v]=low[v]= ++tmr;
    ile++;
    stos.pb(v);
    for(auto w:grf[v]){
        if(w==p) continue;
        if(!pre[w]){
            dfs(w, v);
            low[v]=min(low[v], low[w]);
            if(low[w]>= pre[v]){
                tree[v].pb(n+cnt);
                while(tree[n+cnt].size()==0 || tree[n+cnt].back()!=w){
                    tree[n+cnt].pb(stos.back());
                    stos.pop_back();
                }
                cnt++;
            }
        }else low[v]=min(low[v], pre[w]);
    }
}
void dfs2(int v){
    if(v<=n) siz[v]=1;
    for(auto w:tree[v]){
        dfs2(w);
        siz[v]+=siz[w];
        if(v>n) out-=(ll)tree[v].size()*siz[w]*(siz[w]-1);
    }
    if(v>n) out-=(ll)tree[v].size()*(ile-siz[v])*(ile-siz[v]-1);
}
int main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    int m;
    cin >> n >> m;
    for(int i=0; i<m; i++){
        int a, b;
        cin >> a >> b;
        grf[a].pb(b);
        grf[b].pb(a);
    }
    for(int i=1; i<=n; i++){
        if(pre[i]) continue;
        ile=0;
        dfs(i, i);
        out+=ile*(ile-1)*(ile-2);
        dfs2(i);
    }
    cout << out << '\n';
    return 0;
}

• 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