Submission #879512

#	Time	Username	Problem	Language	Result	Execution time	Memory
879512		marvinthang	Beads and wires (APIO14_beads)	C++17	100 / 100	83 ms	20424 KiB

beads

/*************************************
*    author: marvinthang             *
*    created: 27.11.2023 20:59:10    *
*************************************/

#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 << '}'; }
template <class A, class B> bool minimize(A &a, B b)  { if (a > b) { a = b; return true; } return false; }
template <class A, class B> bool maximize(A &a, B b)  { if (a < b) { a = b; return true; } return false; }

inline char gc() { // like getchar()
	static char buf[1 << 16];
	static size_t bc, be;
	if (bc >= be) {
		buf[0] = 0, bc = 0;
		be = fread(buf, 1, sizeof(buf), stdin);
	}
	return buf[bc++]; // returns 0 on EOF
}

int readInt() {
	int a, c;
	while ((a = gc()) < 40);
	if (a == '-') return -readInt();
	while ((c = gc()) >= 48) a = a * 10 + c - 480;
	return a - 48;
}

// end of template

const int INF = 1e9 + 7;

void process(void) {
	int n = readInt();
	vector <vector <pair <int, int>>> adj(n);	
	REP(i, n - 1) {
		int u = readInt() - 1, v = readInt() - 1, w = readInt();
		adj[u].emplace_back(w, v);
		adj[v].emplace_back(w, u);
	}
	vector <array <array <int, 2>, 2>> dp(n);
	function<void(int)> dfs = [&] (int u) {
		REP(a, 2) REP(b, 2) if (a || b) dp[u][a][b] = -INF;
		for (auto [w, v]: adj[u]) {
			adj[v].erase(find(ALL(adj[v]), pair {w, u}));
			dfs(v);
			REP(b, 2) dp[v][1][b] += w;
			dp[u][0][0] += max(dp[v][0][0], dp[v][1][0]);
		}
		pair <int, int> best_child(-INF, -INF);
		for (auto [w, v]: adj[u]) {
			int cur = max(dp[v][0][0], dp[v][0][1]) - max(dp[v][0][0], dp[v][1][0]) + w;
			if (best_child.fi < cur) best_child.se = best_child.fi, best_child.fi = cur;
			else maximize(best_child.se, cur);
		}
		for (auto [w, v]: adj[u]) {
			maximize(dp[u][0][1], dp[v][0][0] - max(dp[v][0][0], dp[v][1][0]) + w + (max(dp[v][0][0], dp[v][0][1]) - max(dp[v][0][0], dp[v][1][0]) + w == best_child.fi ? best_child.se : best_child.fi) + dp[u][0][0]);
		}
		for (auto [w, v]: adj[u]) {
			maximize(dp[u][0][1], max(dp[v][0][1], dp[v][1][1]) + dp[u][0][0] - max(dp[v][0][0], dp[v][1][0]));
			REP(b, 2) maximize(dp[u][1][b], dp[v][0][b] + w + dp[u][0][0] - max(dp[v][0][0], dp[v][1][0]));
		}
	};
	dfs(0);
	cout << max(dp[0][0][0], dp[0][0][1]) << '\n';
}

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

Compilation message (stderr)

beads.cpp: In function 'int main()':
beads.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); }
      |                                                      ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
beads.cpp:104:2: note: in expansion of macro 'file'
  104 |  file("beads");
      |  ^~~~
beads.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); }
      |                                                                                       ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
beads.cpp:104:2: note: in expansion of macro 'file'
  104 |  file("beads");
      |  ^~~~

• Subtask 1: 13 / 13
• Subtask 2: 15 / 15
• Subtask 3: 29 / 29
• Subtask 4: 43 / 43