제출 #674437

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
674437		ghostwriter	Beads and wires (APIO14_beads)	C++17	100 / 100	176 ms	21472 KiB

beads

// #pragma GCC optimize ("Ofast")
// #pragma GCC target ("avx2")
#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
    #include <debug.h>
#else
    #define debug(...)
#endif
#define ft front
#define bk back
#define st first
#define nd second
#define ins insert
#define ers erase
#define pb push_back
#define pf push_front
#define _pb pop_back
#define _pf pop_front
#define lb lower_bound
#define ub upper_bound
#define mtp make_tuple
#define bg begin
#define ed end
#define all(x) (x).bg(), (x).ed()
#define sz(x) (int)(x).size()
// #define int long long
typedef long long ll; typedef unsigned long long ull;
typedef double db; typedef long double ldb;
typedef pair<int, int> pi; typedef pair<ll, ll> pll;
typedef vector<int> vi; typedef vector<ll> vll; typedef vector<pi> vpi; typedef vector<pll> vpll;
typedef string str;
#define FOR(i, l, r) for (int i = (l); i <= (r); ++i)
#define FOS(i, r, l) for (int i = (r); i >= (l); --i)
#define FRN(i, n) for (int i = 0; i < (n); ++i)
#define FSN(i, n) for (int i = (n) - 1; i >= 0; --i)
#define EACH(i, x) for (auto &i : (x))
#define WHILE while
template<typename T> T gcd(T a, T b) { T d2 = (a | b) & -(a | b); a /= d2; b /= d2; WHILE(b) { a = a % b; swap(a, b); } return a * d2; }
template<typename T> T lcm(T a, T b) { return a / gcd(a, b) * b; }
void _assert(bool statement) { if (statement) return; cerr << "\n>> Assertion failed!\n"; exit(0); }
void _assert(bool statement, const str &message) { if (statement) return; cerr << "\n>> Assertion failed: " << message << '\n'; exit(0); }
void _error(const str &message) { cerr << "\n>> Error: " << message << '\n'; exit(0); }
#define file "TEST"
mt19937 rd(chrono::steady_clock::now().time_since_epoch().count());
ll rand(ll l, ll r) { return uniform_int_distribution<ll>(l, r)(rd); }
/*
----------------------------------------------------------------
    END OF TEMPLATE
----------------------------------------------------------------
    Tran The Bao - ghostwriter
    Training for VOI23 gold medal
----------------------------------------------------------------
    GOAT
----------------------------------------------------------------
*/
const int oo = 1e9 + 5;
const int N = 2e5 + 5;
int n, d[N][2], rs = 0;
vpi adj[N];
void input(int test_id) {
	cin >> n;
	FOR(i, 1, n - 1) {
		int a, b, c;
		cin >> a >> b >> c;
		adj[a].pb({b, c});
		adj[b].pb({a, c});
	}
}
void dfs(int u, int p) {
	int sum = 0;
	EACH(j, adj[u]) {
		int v = j.st, w = j.nd;
		if (v == p) continue;
		dfs(v, u);
		d[u][0] += max(d[v][0], d[v][1] + w);
		sum += max(d[v][0], d[v][1] + w);
	}
	d[u][1] = -oo;
	EACH(j, adj[u]) {
		int v = j.st, w = j.nd;
		if (v == p) continue;
		d[u][1] = max(d[u][1], sum - max(d[v][0], d[v][1] + w) + d[v][0] + w);
	}
	// debug(u, 0, d[u][0]);
	// debug(u, 1, d[u][1]);
}
void dfs1(int u, int p, int pw, int d0, int d1) {
	int max1 = -oo, max2 = -oo;
	auto updm = [&](int v) {
		if (max1 < v) {
			max2 = max1;
			max1 = v;
		}
		else max2 = max(max2, v);
	};
	if (p) updm(d0 + pw - max(d0, d1 + pw));
	rs = max(rs, d[u][0] + max(d0, d1 + pw));
	int sum = 0;
	EACH(j, adj[u]) {
		int v = j.st, w = j.nd;
		if (v == p) continue;
		sum += max(d[v][0], d[v][1] + w);
		updm(d[v][0] + w - max(d[v][0], d[v][1] + w));
	}
	EACH(j, adj[u]) {
		int v = j.st, w = j.nd;
		if (v == p) continue;
		int s0 = sum - max(d[v][0], d[v][1] + w) + max(d0, d1 + pw), s1 = s0;
		if (max1 == d[v][0] + w - max(d[v][0], d[v][1] + w)) s1 += max2;
		else s1 += max1;
		dfs1(v, u, w, s0, s1);
	}
}
void solve(int test_id) {
	dfs(1, 0);
	dfs1(1, 0, 0, 0, 0);
	cout << rs;
}
void reinit(int test_id) {

}
signed main() {
    ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
    // freopen(file".inp", "r", stdin);
    // freopen(file".out", "w", stdout);
    int test_num = 1;
    // cin >> test_num; // comment if the problem does not requires multitest
    FOR(i, 1, test_num) {
        input(i); // input in noninteractive problems for case #i
        solve(i); // main function to solve case #i
        reinit(i); // reinit global data to default used in case #i
    }
    #ifdef LOCAL
        cerr << "\nTime: " << setprecision(5) << fixed << (ldb)clock() / CLOCKS_PER_SEC << "ms.\n";
    #endif
    return 0;
}
/*
10
4 10 2
1 2 21
1 3 13
6 7 1
7 9 5
2 4 3
2 5 8
1 6 55
6 8 34
----------------------------------------------------------------
From Benq:
    stuff you should look for
        * int overflow, array bounds
        * special cases (n=1?)
        * do smth instead of nothing and stay organized
        * WRITE STUFF DOWN
        * DON'T GET STUCK ON ONE APPROACH
----------------------------------------------------------------
*/

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