Submission #974309

#	Time	Username	Problem	Language	Result	Execution time	Memory
974309		vjudge1	Duathlon (APIO18_duathlon)	C++17	0 / 100	1103 ms	1048576 KiB

count_triplets

#include <bits/stdc++.h>

#define lli long long int
#define ld long double
#define pb push_back
#define MP make_pair
#define REP(i, n) for(int i = 0; (i) < (n); (i)++)
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()

using namespace std;

void fastio() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
}

const int N = 1e5 + 5;
const int INF = 1e9 + 500;
int n, m;
vector<vector<array<int, 2> > > adj(N, vector<array<int, 2> >());
int tim = 0;
vector<int> tin(N, -1), low(N, 0);
vector<array<int, 2> > edg(N);
vector<bool> isBr(N, 0);
vector<int> comp(N, -1), cmpsz(N, 0);
vector<vector<int> > cadj(N, vector<int>());
vector<int> subsz(N, 0);
lli ans = 0;
void find_bridge(int node, int par) {
    tin[node] = low[node] = tim++;
    for(auto c : adj[node]) {
        if(c[0] == par) {
            continue;
        }
        if(tin[c[0]] != -1) {
            low[node] = min(low[node], tin[c[0]]);
        }
        else {
            find_bridge(c[0], node);
            low[node] = min(low[node], low[c[0]]);
            if(low[c[0]] > tin[node]) {
                //bridge
                isBr[c[1]] = 1;
            }
        }
    }
}

void get_comp(int node, int par, int cm) {
    comp[node] = cm;
    cmpsz[cm]++;
    for(auto c : adj[node]) {
        if(c[0] == par || isBr[c[1]]) continue;
        get_comp(c[0], node, cm);
    }
}

void prec(int node, int par) {
    subsz[node] = cmpsz[node];
    for(auto c : cadj[node]) {
        if(c == par) continue;
        prec(c, node);
        subsz[node] += subsz[c];
    }
}

void dfs(int node, int par) {
    lli ret = 0;
    lli x = n - cmpsz[node];
    for(auto c : cadj[node]) {
        if(c == par) {
            int sbt = n - subsz[node];
            ret += 1ll * cmpsz[node] * sbt * (x - sbt); 
            continue;
        }
        int sbt = subsz[c];
        ret += 1ll * cmpsz[node] * sbt * (x - sbt);
        dfs(c, node);
    }
    ans += ret;
}


void solve() {
    cin >> n >> m;
    REP(i, m) {
        int u, v;
        cin >> u >> v;
        edg[i] = {u, v};
        adj[u].pb({v, i});
        adj[v].pb({u, i});
    }    
    find_bridge(1, 0);
    int cur = 1;
    for(int i = 1; i <= n; i++) {
        if(comp[i] == -1) {
            get_comp(i, 0, cur++);
        }
        // cout << "i:" << i << " comp:" << comp[i] << "\n";
    }
    for(int i = 0; i < m; i++) {
        if(isBr[i]) {
            // cout << edg[i][0] << " " << edg[i][1] << "\n";
            cadj[comp[edg[i][0]]].pb(edg[i][1]);
            cadj[comp[edg[i][1]]].pb(edg[i][0]);
        }
    }
    prec(1, 0);
    for(int i = 1; i < cur; i++) {
        ans += 1ll * cmpsz[i] * (cmpsz[i] - 1) * (cmpsz[i] - 2);
    }
    dfs(1, 0);
    cout << ans << "\n";
}


signed main() {
    fastio();
    solve();
}

• Subtask 1: 0 / 5
• Subtask 2: 0 / 11
• Subtask 3: 0 / 8
• Subtask 4: 0 / 10
• Subtask 5: 0 / 13
• Subtask 6: 0 / 15
• Subtask 7: 0 / 20
• Subtask 8: 0 / 8
• Subtask 9: 0 / 10