Submission #958083

#	Time	Username	Problem	Language	Result	Execution time	Memory
958083		MinaRagy06	Beads and wires (APIO14_beads)	C++17	0 / 100	3 ms	15960 KiB

beads

#include <bits/stdc++.h>
using namespace std;
#define ll long long
 
const int N = 200'005;
const ll inf = 1e18;
ll dp[N][2][2];
vector<array<ll, 2>> tadj[N], adj[N];
void build(int i, int p) {
	adj[i].clear();
	for (auto [nxt, w] : tadj[i]) {
		if (nxt == p) continue;
		build(nxt, i);
		adj[i].push_back({nxt, w});
	}
}
ll dfs(int i, int st, int carry) {
	if (~dp[i][st][carry]) {
		return dp[i][st][carry];
	}
	ll ans = 0;
	if (carry) {
		ans = -inf;
	}
	for (int f = 0; f < 2; f++) {
		ll s = 0;
		for (auto [nxt, w] : adj[i]) {
			s += max(dfs(nxt, 1, 1) + w, (carry || f? 0ll : dfs(nxt, 0, 0)));
		}
		if (!carry) {
			ans = max(ans, s);
		} else {
			for (auto [nxt, w] : adj[i]) {
				ans = max(ans, s - max(dfs(nxt, 1, 1) + w, (carry || f? 0ll : dfs(nxt, 0, 0))) + dfs(nxt, 1, 0) + w);
			}
		}
// 		ll mx[2] = {-inf, -inf};
// 		for (auto [nxt, w] : adj[i]) {
// 			ll v = - max(dfs(nxt, 1, 1) + w, (carry || f? 0ll : dfs(nxt, 0, 0))) + dfs(nxt, 1, 0) + w;
// 			if (v > mx[1]) {
// 				mx[1] = v;
// 			}
// 			if (mx[0] < mx[1]) swap(mx[0], mx[1]);
// 		}
	}
	return dp[i][st][carry] = ans;
}
int main() {
	ios_base::sync_with_stdio(0), cin.tie(0);
	memset(dp, -1, sizeof dp);
	int n;
	cin >> n;
	for (int i = 1, u, v, w; i < n; i++) {
		cin >> u >> v >> w;
		tadj[u].push_back({v, w});
		tadj[v].push_back({u, w});
	}
	ll ans = 0;
	for (int i = 1; i <= n; i++) {
		build(i, 0);
		ans = max(ans, dfs(i, 0, 0));
	}
	cout << ans << '\n';
	return 0;
}

• Subtask 1: 0 / 13
• Subtask 2: 0 / 15
• Subtask 3: 0 / 29
• Subtask 4: 0 / 43