Submission #371473

#	Time	Username	Problem	Language	Result	Execution time	Memory
371473		Leonardo_Paes	Duathlon (APIO18_duathlon)	C++17	100 / 100	143 ms	26860 KiB

count_triplets

#include <bits/stdc++.h>
using namespace std;
//#define int long long
#define ar array
#define sz(a) ((int)(a).size())
#define all(a) (a).begin(),(a).end()
typedef long long ll;
typedef pair<int,int> pii;
#define f first
#define s second
const int maxn = 1e5+10;
vector<int> grafo[maxn], bcc[2*maxn];
int n, m, in[maxn], low[maxn], sub[2*maxn], t, sz, bccs = 1; // tempo de entrada e menor tempo de entrada de back-edge
stack<int> s;

void dfs(int u, int p = 0){
    in[u] = low[u] = ++t;
    s.push(u);
    ++sz;
    for(int v : grafo[u]){
        if(v == p) continue;
        if(!in[v]){
            dfs(v, u);
            low[u] = min(low[u], low[v]);
            if(low[v] >= in[u]){
                int id = n + bccs;
                bcc[u].push_back(id);
                while(bcc[id].empty() or bcc[id].back() != v){
                    bcc[id].push_back(s.top());
                    s.pop();
                }
                bccs++;
            }
        }
        else low[u] = min(low[u], in[v]);
    }
}

ll solve(int u){
    ll ans = 0, tam;
    sub[u] = (u <= n);
    tam = (ll)bcc[u].size();
    for(int v : bcc[u]){
        ans += solve(v);
        sub[u] += sub[v];
        if(u > n) ans += tam * sub[v] * (sub[v] - 1);
    }
    if(u > n) ans += tam * (sz - sub[u]) * (sz - sub[u] - 1);
    return ans;
}

int32_t main(){
    ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
    cin >> n >> m;
    for(int i=1; i<=m; i++){
        int u, v;
        cin >> u >> v;
        grafo[u].push_back(v);
        grafo[v].push_back(u);
    }
    ll ans = 0;
    for(int i=1; i<=n; i++){
        if(!in[i]){
            sz = 0;
            dfs(i);
            ans += 1LL * sz * (sz-1) * (sz-2); // total
            ans -= solve(i); // triplas ruins
        }
    }
    cout << ans << "\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