Submission #33478

#	Time	Username	Problem	Language	Result	Execution time	Memory
33478		szawinis	Beads and wires (APIO14_beads)	C++14	0 / 100	7 ms	5120 KiB

beads

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int N = 2e5+1;
const ll INF = 1e12+1;

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

void dfs(int u, int par) {
	for(auto p: g[u]) if(p.first != par) dfs(p.first, u);
	vector<int> v, w, vals;
	for(auto p: g[u]) if(p.first != par) {
		v.push_back(p.first);
		w.push_back(p.second);
		vals.push_back(max(dp[p.first][1] + p.second, dp[p.first][0]));
	}

	dp[u][1] = -INF;
	ll sum = 0;
	for(int i = 0; i < v.size(); i++) sum += vals[i];
	for(int i = 0; i < v.size(); i++) dp[u][1] = max(sum + dp[v[i]][0] + w[i] - vals[i], dp[u][1]);

	dp[u][0] = sum;
	ll mx = -INF;
	for(int i = 0; i < v.size(); i++) {
		dp[u][0] = max(sum + mx + dp[v[i]][0] + w[i] - vals[i], dp[u][0]);
		mx = max(dp[v[i]][0] + w[i] - vals[i], mx);
	}
	// cout << u << ' ' << dp[u][0] << ' ' << dp[u][1] <<endl;
}

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	cin >> n;
	for(int i = 1, u, v, w; i < n; i++) {
		cin >> u >> v >> w;
		g[u].emplace_back(v, w);
		g[v].emplace_back(u, w);
	}
	dfs(1, 0);
	cout << dp[1][0];
}

Compilation message (stderr)

beads.cpp: In function 'void dfs(int, int)':
beads.cpp:22:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i = 0; i < v.size(); i++) sum += vals[i];
                 ~~^~~~~~~~~~
beads.cpp:23:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i = 0; i < v.size(); i++) dp[u][1] = max(sum + dp[v[i]][0] + w[i] - vals[i], dp[u][1]);
                 ~~^~~~~~~~~~
beads.cpp:27:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i = 0; i < v.size(); i++) {
                 ~~^~~~~~~~~~

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