Submission #874452

#	Time	Username	Problem	Language	Result	Execution time	Memory
874452		marvinthang	Duathlon (APIO18_duathlon)	C++17	100 / 100	121 ms	38232 KiB

count_triplets

/*************************************
*    author: marvinthang             *
*    created: 17.11.2023 11:19:17    *
*************************************/

#include <bits/stdc++.h>

using namespace std;

#define                  fi  first
#define                  se  second
#define                left  ___left
#define               right  ___right
#define                TIME  (1.0 * clock() / CLOCKS_PER_SEC)
#define             MASK(i)  (1LL << (i))
#define           BIT(x, i)  ((x) >> (i) & 1)
#define  __builtin_popcount  __builtin_popcountll
#define              ALL(v)  (v).begin(), (v).end()
#define           REP(i, n)  for (int i = 0, _n = (n); i < _n; ++i)
#define          REPD(i, n)  for (int i = (n); i-- > 0; )
#define        FOR(i, a, b)  for (int i = (a), _b = (b); i < _b; ++i) 
#define       FORD(i, b, a)  for (int i = (b), _a = (a); --i >= _a; ) 
#define       FORE(i, a, b)  for (int i = (a), _b = (b); i <= _b; ++i) 
#define      FORDE(i, b, a)  for (int i = (b), _a = (a); i >= _a; --i) 
#define        scan_op(...)  istream & operator >> (istream &in, __VA_ARGS__ &u)
#define       print_op(...)  ostream & operator << (ostream &out, const __VA_ARGS__ &u)
#ifdef LOCAL
    #include "debug.h"
#else
    #define file(name) if (fopen(name".inp", "r")) { freopen(name".inp", "r", stdin); freopen(name".out", "w", stdout); }
    #define DB(...) 23
    #define db(...) 23
    #define debug(...) 23
#endif

template <class U, class V> scan_op(pair <U, V>)  { return in >> u.first >> u.second; }
template <class T> scan_op(vector <T>)  { for (size_t i = 0; i < u.size(); ++i) in >> u[i]; return in; }
template <class U, class V> print_op(pair <U, V>)  { return out << '(' << u.first << ", " << u.second << ')'; }
template <size_t i, class T> ostream & print_tuple_utils(ostream &out, const T &tup) { if constexpr(i == tuple_size<T>::value) return out << ")";  else return print_tuple_utils<i + 1, T>(out << (i ? ", " : "(") << get<i>(tup), tup); }
template <class ...U> print_op(tuple<U...>) { return print_tuple_utils<0, tuple<U...>>(out, u); }
template <class Con, class = decltype(begin(declval<Con>()))> typename enable_if <!is_same<Con, string>::value, ostream&>::type operator << (ostream &out, const Con &con) { out << '{'; for (__typeof(con.begin()) it = con.begin(); it != con.end(); ++it) out << (it == con.begin() ? "" : ", ") << *it; return out << '}'; }

// end of template

void process(void) {
	int n, m; cin >> n >> m;
	vector <vector <int>> adj(n), child(n), tree_adj(n + n);
	vector <pair <int, int>> edges;
	REP(i, m) {
		int u, v; cin >> u >> v; --u; --v;
		adj[u].push_back(i);
		adj[v].push_back(i);
		edges.emplace_back(u, v);
	}
	vector <int> low(n), num(n);
	vector <bool> used(m);
	int nv = 0;
	function <void(int)> dfs = [&] (int u) {
		static int tt = 0;
		num[u] = ++tt;
		low[u] = n + 1;
		++nv;
		for (int id: adj[u]) if (!used[id]) {
			used[id] = true;
			int v = edges[id].fi ^ edges[id].se ^ u;
			if (!num[v]) {
				dfs(v);
				low[u] = min(low[u], low[v]);
				child[u].push_back(v);
			} else low[u] = min(low[u], num[v]);
		}
	};
	int bc_idx = n;
	function <void(int, int)> build_tree = [&] (int u, int cur_bc) {
		if (cur_bc >= 0) {
			tree_adj[u].push_back(cur_bc);
			tree_adj[cur_bc].push_back(u);
		}
		for (int v: child[u]) {
			if (low[v] >= num[u]) {
				tree_adj[u].push_back(bc_idx);
				tree_adj[bc_idx].push_back(u);
				build_tree(v, bc_idx++);
			} else build_tree(v, cur_bc);
		}
	};

	vector <int> sz(n + n);
	vector <long long> sum_pair(n + n);
	function <void(int, int)> count_pair = [&] (int u, int par) {
		sz[u] = u < n;
		for (int v: tree_adj[u]) if (v != par) {
			count_pair(v, u);
			sz[u] += sz[v];
		}
		if (u < n) return;
		for (int v: tree_adj[u]) {
			int t = v == par ? nv - sz[u] : sz[v];
			sum_pair[u] += 1LL * t * (t - 1);
		}
	};

	long long res = 0;
	function <void(int, int)> solve = [&] (int u, int par) {
		if (u < n) {
			res += 1LL * (nv - 1) * (nv - 2);
			for (int v: tree_adj[u]) {
				int t = v == par ? sz[u] : nv - sz[v];
				res -= sum_pair[v] - 1LL * t * (t - 1);
			}
		}
		for (int v: tree_adj[u]) if (v != par) solve(v, u);
	};

	REP(i, n) if (!num[i]) {
		nv = 0;
		dfs(i);
		build_tree(i, -1);
		count_pair(i, -1);
		solve(i, -1);
	}
	cout << res << '\n';
}

int main(void) {
	ios_base::sync_with_stdio(false); cin.tie(nullptr); // cout.tie(nullptr);
	file("duathlon");
	// int t; cin >> t; while (t--)
	process();
	// cerr << "Time elapsed: " << TIME << " s.\n";
	return (0^0);
}

Compilation message (stderr)

count_triplets.cpp: In function 'int main()':
count_triplets.cpp:30:61: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   30 |     #define file(name) if (fopen(name".inp", "r")) { freopen(name".inp", "r", stdin); freopen(name".out", "w", stdout); }
      |                                                      ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
count_triplets.cpp:127:2: note: in expansion of macro 'file'
  127 |  file("duathlon");
      |  ^~~~
count_triplets.cpp:30:94: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   30 |     #define file(name) if (fopen(name".inp", "r")) { freopen(name".inp", "r", stdin); freopen(name".out", "w", stdout); }
      |                                                                                       ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
count_triplets.cpp:127:2: note: in expansion of macro 'file'
  127 |  file("duathlon");
      |  ^~~~

• 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