Submission #402949

#	Time	Username	Problem	Language	Result	Execution time	Memory
402949		Drew_	Beads and wires (APIO14_beads)	C++17	0 / 100	5 ms	5016 KiB

beads

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

#define pb push_back
#define ii pair<int, int>
#define f1 first
#define s2 second

const int MAX = 2e5 + 69;

int n;
vector<ii> adj[MAX];

//DP[X][0]: vertex X, not using the edge from parent
//DP[X][1]: vertex X, using the edge from parent
int dp[MAX][2];
int cost[MAX];
void dfs(int node, int par, int parw)
{
	int ctr = 0; //point for using 0 edge (X as centre)
	vector<int> v; //bonus point for using the edge (must free the child's parent edge)
	for (auto [to, w] : adj[node])
	{
		if (to != par)
		{
			dfs(to, node, w);

			ctr += max(dp[to][0], dp[to][1]);
			if (dp[to][0] >= dp[to][1])
				v.pb(w);
			else v.pb(dp[to][0] - dp[to][1] + w);
		}
	}
	if (v.empty()) // a leaf
		return;

	sort(v.begin(), v.end(), greater<int>());
	dp[node][0] = ctr;
	dp[node][1] = ctr + v[0] + parw;
	if (v.size() >= 2)
		dp[node][0] = max(dp[node][0], ctr + v[0] + v[1]);
}

int main()
{
	ios :: sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);

	cin >> n;
	for (int i = 0; i < n-1; ++i)
	{
		int u, v, w;
		cin >> u >> v >> w;

		adj[u].pb({v, w}); adj[v].pb({u, w});
	}

	dfs(1, -1, -1);
	cout << dp[1][0] << '\n';
	return 0;
}

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