Submission #958055

#	Time	Username	Problem	Language	Result	Execution time	Memory
958055		MinaRagy06	Beads and wires (APIO14_beads)	C++17	0 / 100	4 ms	11356 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>> adj[N];
void build(int i, int p) {
	vector<array<ll, 2>> newadj;
	for (auto [nxt, w] : adj[i]) {
		if (nxt == p) continue;
		build(nxt, i);
		newadj.push_back({nxt, w});
	}
	adj[i] = newadj;
}
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;
	}
	if (!st) {
		for (auto [nxt, w] : adj[i]) {
			ans = max(ans, dfs(nxt, 0, 0));
		}
	}
	ll s = 0;
	for (auto [nxt, w] : adj[i]) {
		s += max(dfs(nxt, 1, 1) + w, 0ll);
	}
	if (!carry) {
		ans = max(ans, s);
	} else {
		for (auto [nxt, w] : adj[i]) {
			ans = max(ans, s - max(dfs(nxt, 1, 1) + w, 0ll) + dfs(nxt, 1, 0) + w);
		}
	}
	ll mx[2] = {-inf, -inf};
	for (auto [nxt, w] : adj[i]) {
		ll v = - max(dfs(nxt, 1, 1) + w, 0ll) + dfs(nxt, 1, 0) + w;
		if (v > mx[1]) {
			mx[1] = v;
		}
		if (mx[0] < mx[1]) swap(mx[0], mx[1]);
	}
	ans = max(ans, s + 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;
		adj[u].push_back({v, w});
		adj[v].push_back({u, w});
	}
	build(1, 0);
	cout << dfs(1, 0, 0) << '\n';
	return 0;
}

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