Submission #1094140

#	Time	Username	Problem	Language	Result	Execution time	Memory
1094140		BF001	Duathlon (APIO18_duathlon)	C++17	100 / 100	72 ms	29608 KiB

count_triplets

#include<bits/stdc++.h>
using namespace std;
 
#define N 100005
#define int long long

int low[N], id[N], cnt, siz[2 * N], n, m, res = 0, bcc, sizncc;
vector<int> adj[N], adj2[2 * N];
stack<int> st;

void dfs(int u, int p){
    low[u] = id[u] = ++cnt;
    sizncc++;
    st.push(u);
    for (auto x : adj[u]){
        if (x == p){
            p = -1;
            continue;
        }
        if (id[x]){
            low[u] = min(low[u], id[x]);
        }
        else{
            dfs(x, u);
            low[u] = min(low[u], low[x]);
            if (low[x] >= id[u]){
                bcc++;
                int s = -1;
                adj2[u].push_back(bcc);
                while (s != x){
                    s = st.top();
                    st.pop();
                    low[s] = id[s] = n + 1;
                    adj2[bcc].push_back(s);
                }
            }
        }
    }
}

void cal(int u, int p){
    int si = (int) adj2[u].size();
    siz[u] = (u <= n);
    for (auto x : adj2[u]){
        if (x == p) continue;
        cal(x, u);
        siz[u] += siz[x];
        if (u > n){
            res -= si * siz[x] * (siz[x] - 1);
        }
    }
    if (u > n) res -= si * (sizncc - siz[u]) * (sizncc - siz[u] - 1);
}
 
signed main(){
    ios_base::sync_with_stdio(0);
    cin.tie(NULL);
 
    cin >> n >> m;
    bcc = n;
    for (int i = 1; i <= m; i++){
        int u, v;
        cin >> u >> v;
        adj[u].push_back(v);
        adj[v].push_back(u);
    }

    for (int i = 1; i <= n; i++){
        if (!id[i]){
            sizncc = 0;
            dfs(i, 0);
            res += sizncc * (sizncc - 1) * (sizncc - 2);
            cal(i, 0);
        }
    }
 
    cout << res;
    
    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