Submission #453241

#	Time	Username	Problem	Language	Result	Execution time	Memory
453241		valerikk	Beads and wires (APIO14_beads)	C++17	28 / 100	1075 ms	972 KiB

beads

#include <iostream>
#include <vector>
#include <algorithm>
#include <set>

using namespace std;

typedef long long ll;

const int N = 10010;
const int INF = 2e9;

int n;
vector<pair<int, int>> g[N];
int dp[N][2];
int up[N][2];

void dfs(int v, int p = -1, int pc = 0) {
	int mx = -INF, sum = 0;
	for (auto [u, c] : g[v]) {
		if (u != p) {
			dfs(u, v, c);
			sum += dp[u][1];
			mx = max(mx, dp[u][0] - dp[u][1] + c);
		}
	}
	dp[v][0] = sum;
	dp[v][1] = sum + max(0, mx + pc);
}

void dfs_up(int v, int p = -1, int pc = 0) {
	int sum = 0;
	multiset<int> st;
	if (p != -1) {
		sum += up[v][0];
		st.insert(up[v][0] - up[v][1] + pc);
	}
	for (auto [u, c] : g[v]) {
		if (u != p) {
			sum += dp[u][0];
			st.insert(dp[u][0] - dp[u][1] + c);
		}
	}
	for (auto [u, c] : g[v]) {
		if (u != p) {
			sum -= dp[u][0];
			st.erase(st.find(dp[u][0] - dp[u][1] + c));
			up[u][0] = sum;
			up[u][1] = sum + (st.empty() ? 0 : max(0, *st.rbegin() + c));
			dfs_up(u, v, c);
			sum += dp[u][0];
			st.insert(dp[u][0] - dp[u][1] + c);
		}
	}
}

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	cin >> n;
	for (int i = 0; i < n - 1; ++i) {
		int a, b;
		ll c;
		cin >> a >> b >> c;
		g[a].push_back({b, c});
		g[b].push_back({a, c});
	}
	if (0) {
		dfs(1);
		dfs_up(1);
		int ans = 0;
		for (int i = 1; i <= n; ++i) {
			ans = max(ans, dp[i][0] + max(up[i][0], up[i][1]));
		}
		cout << ans << endl;
	} else {
		int ans = 0;
		for (int i = 1; i <= n; ++i) {
			dfs(i);
			ans = max(ans, dp[i][0]);
		}
		cout << ans << endl;
	}
	return 0;
}

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