Submission #995632

#	Time	Username	Problem	Language	Result	Execution time	Memory
995632		NoLove	Duathlon (APIO18_duathlon)	C++14	100 / 100	67 ms	32020 KiB

count_triplets

/**
 *    author : Lăng Trọng Đạt
 *    created: 09-06-2024 
**/
#include <bits/stdc++.h>
using namespace std;
#ifndef LANG_DAT
#define db(...) ;
#endif // LANG_DAT
#define int long long
#define mp make_pair
#define f first
#define se second
#define pb push_back
#define all(v) (v).begin(), (v).end()
using pii = pair<int, int>;
using vi = vector<int>;
#define FOR(i, a, b) for (int (i) = a; (i) <= (b); i++)
void mx(int& a, int b) { if (b > a) a = b; }
void mi(int& a, int b) { if (b < a) a = b; }
#define si(x) (int)(x.size())
const int INF = 1e18;
const int MOD = 1e9 + 7;


/*
    1. Init (input graph)
    2. Finding all cut vertex
    3. Transform graph into block-cut tree
    4. Calculate subsize of each node (in block-cut tree)
*/

const int MAXN = 2e5 + 5;
int g[MAXN];
int n, m, a, b;

vi adj[MAXN];
int timer = 1;
bool ap[MAXN];
int id[MAXN], low[MAXN];
int bad = 0;
vi path;

vi bcc_adj[MAXN];
int bcc_num = 1;
int N = 0;
void dfs(int v, int prv) {
    N++;
    path.pb(v);
    id[v] = low[v] = timer++;
    for (int u : adj[v]) {
        if (u == prv) continue;
        if (id[u]) mi(low[v], id[u]);
        else {
            dfs(u, v);
            mi(low[v], low[u]);
            if (id[v] <= low[u]) {
                db(v, u, low[u], id[v], bcc_num)
                bcc_adj[v].pb(bcc_num + n);
                while (bcc_adj[bcc_num + n].empty() || bcc_adj[bcc_num + n].back() != u) {
                    bcc_adj[bcc_num + n].pb(path.back());
                    path.pop_back();
                }
                bcc_num++;
            }
        }
    }
}
int ans = 0;
int sz[MAXN];
void dfs2(int v, int prv) {
    if (v <= n) sz[v] = 1;
    for (int u : bcc_adj[v]) {
        // if (u == prv) continue;
        dfs2(u, v);
        sz[v] += sz[u];
        if (v > n) ans -= si(bcc_adj[v]) * sz[u] * (sz[u] - 1); // v is change
    }
    if (v > n) ans -= si(bcc_adj[v]) * (N - sz[v]) * (N - sz[v] - 1); 
    db(ans, v, sz[v])
}
void init() {
    cin >> n >> m;
    FOR(i, 1, m) {
        cin >> a >> b;
        adj[a].pb(b);
        adj[b].pb(a);
    }
    FOR(i, 1, n) {
        if (!id[i]) {
            N = 0;
            dfs(i, -1);
            ans += N * (N - 1) * (N - 2);
            db(i, ans, N)
            dfs2(i, -1);
        }
    }
    // FOR(i, 1, n + bcc_num) {
    //     for (int u : bcc_adj[i]) {
    //         cout << i << " " << u << "\n";
    //     }
    // }
}

int32_t main() {
    cin.tie(0)->sync_with_stdio(0);
    if (fopen("hi.inp", "r")) {
        freopen("hi.inp", "r", stdin);
//        freopen("hi.out", "w", stdout);
    } 

    init();   
    cout << ans;
}

Compilation message (stderr)

count_triplets.cpp: In function 'void init()':
count_triplets.cpp:18:31: warning: unnecessary parentheses in declaration of 'i' [-Wparentheses]
   18 | #define FOR(i, a, b) for (int (i) = a; (i) <= (b); i++)
      |                               ^
count_triplets.cpp:84:5: note: in expansion of macro 'FOR'
   84 |     FOR(i, 1, m) {
      |     ^~~
count_triplets.cpp:18:31: warning: unnecessary parentheses in declaration of 'i' [-Wparentheses]
   18 | #define FOR(i, a, b) for (int (i) = a; (i) <= (b); i++)
      |                               ^
count_triplets.cpp:89:5: note: in expansion of macro 'FOR'
   89 |     FOR(i, 1, n) {
      |     ^~~
count_triplets.cpp: In function 'int32_t main()':
count_triplets.cpp:108:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  108 |         freopen("hi.inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~

• 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