제출 #229727

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
229727		lyc	철인 이종 경기 (APIO18_duathlon)	C++14	100 / 100	173 ms	28664 KiB

count_triplets

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

#define TRACE(x) cerr << #x << " :: " << x << endl
#define _ << " " <<
#define SZ(x) (int)(x).size()
#define ALL(x) (x).begin(),(x).end()
#define FOR(i,a,b) for(int i=(a);i<=(b);++i)
#define RFOR(i,a,b) for (int i=(a);i>=(b);--i)

const int MX_N = 1e5+5;
const int MX_M = 2e5+5;

int N, M;
vector<int> al[MX_N];

namespace BCT {
    int pre[MX_N], low[MX_N], dfc, sz;
    int stk[MX_N], tp;

    int wgh[2*MX_N], cnt;
    vector<int> T[2*MX_N];

    int sub[2*MX_N];
    long long ans;

    void Tarjan(int u) {
        pre[u] = low[u] = ++dfc;
        stk[++tp] = u;
        ++sz;
        for (int v : al[u]) {
            if (!pre[v]) {
                Tarjan(v);
                low[u] = min(low[u],low[v]);
                if (low[v] == pre[u]) {
                    wgh[++cnt] = 0;
                    for (int x = 0; x != v; --tp) {
                        x = stk[tp];
                        T[cnt].push_back(x);
                        T[x].push_back(cnt);
                        ++wgh[cnt];
                    }
                    T[cnt].push_back(u);
                    T[u].push_back(cnt);
                    ++wgh[cnt];
                }
            } else low[u] = min(low[u],pre[v]);
        }
    }

    void dfs(int u, int p) {
        long long cur = 0;
        sub[u] = (u<=N);
        for (int v : T[u]) if (v != p) {
            dfs(v,u);
            cur += 2LL * wgh[u] * sub[u] * sub[v];
            sub[u] += sub[v];
        }
        cur += 2LL * wgh[u] * sub[u] * (sz - sub[u]);
        //TRACE(u _ p _ sz _ sub[u] _ cur);
        ans += cur;
    }

    long long solve() {
        fill_n(pre,N+1,0); dfc = tp = 0;
        fill_n(wgh,N+1,-1); ans = 0;
        cnt = N;
        FOR(i,1,N) if (!pre[i]) {
            sz = 0;
            Tarjan(i), --tp;
            dfs(i,0);
        }
        return ans;
    }

    void dbg() {
        FOR(i,1,cnt) {
            cout << i << " sz " << wgh[i] << " :: ";
            for (auto& x : T[i]) cout << x << ' ';
            cout << endl;
        }
    }
};

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

    cin >> N >> M;
    FOR(i,1,M){
        int U, V; cin >> U >> V;
        al[U].push_back(V);
        al[V].push_back(U);
    }

    cout << BCT::solve() << '\n';
    //BCT::dbg();
}

• 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