Submission #389434

#	Time	Username	Problem	Language	Result	Execution time	Memory
389434		phathnv	Duathlon (APIO18_duathlon)	C++11	100 / 100	149 ms	29304 KiB

count_triplets

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;

const int N = 2e5 + 7;

int n, m, sz, cnt[N], low[N], num[N], timer, numComp;
vector<int> adj[N], adj2[N];
stack<int> st;
ll answer;

void Dfs1(int u){
    low[u] = num[u] = ++timer;
    st.push(u);
    sz++;
    for(int v : adj[u]){
        if (!num[v]){
            Dfs1(v);
            low[u] = min(low[u], low[v]);
            if (low[v] == num[u]){
                ++numComp;
                adj2[u].push_back(n + numComp);
                while (true){
                    int vex = st.top();
                    st.pop();
                    adj2[n + numComp].push_back(vex);
                    if (vex == v)
                        break;
                }
            }
        } else {
            low[u] = min(low[u], num[v]);
        }
    }
}

void Dfs2(int u){
    cnt[u] = (u <= n);
    for(int v : adj2[u]){
        Dfs2(v);
        cnt[u] += cnt[v];
        if (u > n)
            answer -= (ll) adj2[u].size() * cnt[v] * (cnt[v] - 1);
    }
    if (u > n)
        answer -= (ll) adj2[u].size() * (sz - cnt[u]) * (sz - cnt[u] - 1);
}

int main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    cin >> n >> m;
    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 (num[i])
            continue;
        sz = 0;
        Dfs1(i);
        Dfs2(i);
        answer += (ll) sz * (sz - 1) * (sz - 2);
    }

    cout << answer;
    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