Submission #33484

#	Time	Username	Problem	Language	Result	Execution time	Memory
33484		szawinis	Beads and wires (APIO14_beads)	C++14	100 / 100	242 ms	29300 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][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][0] + p.second, dp[p.first][0][0]));
	}
	//init
	dp[u][0][1] = dp[u][1][0] = dp[u][1][1] = -INF;

	// 00
	for(int i = 0; i < v.size(); i++) dp[u][0][0] += vals[i];

	//01
	ll mx = -INF;
	for(int i = 0; i < v.size(); i++) mx = max(max(dp[v[i]][0][1], dp[v[i]][1][1] + w[i]) - vals[i], mx);
	dp[u][0][1] = dp[u][0][0] + mx;
	mx = -INF;
	for(int i = 0; i < v.size(); i++) {
		dp[u][0][1] = max(dp[u][0][0] + dp[v[i]][0][0] + w[i] - vals[i] + mx, dp[u][0][1]);
		mx = max(max(dp[v[i]][0][0], dp[v[i]][0][1]) + w[i] - vals[i], mx);
	}
	mx = -INF;
	for(int i = v.size()-1; i >= 0; i--) {
		dp[u][0][1] = max(dp[u][0][0] + dp[v[i]][0][0] + w[i] - vals[i] + mx, dp[u][0][1]);
		mx = max(max(dp[v[i]][0][0], dp[v[i]][0][1]) + w[i] - vals[i], mx);
	}

	//10
	mx = -INF;
	for(int i = 0; i < v.size(); i++) mx = max(dp[v[i]][0][0] + w[i] - vals[i], mx);
	dp[u][1][0] = dp[u][0][0] + mx;

	//11
	mx = -INF;
	for(int i = 0; i < v.size(); i++) mx = max(dp[v[i]][0][1] + w[i] - vals[i], mx);
	dp[u][1][1] = dp[u][0][0] + mx;
	mx = -INF;
	for(int i = 0; i < v.size(); i++) {
		dp[u][1][1] = max(dp[u][0][0] + dp[v[i]][1][0] + w[i] - vals[i] + mx, dp[u][1][1]);
		mx = max(dp[v[i]][0][1] - vals[i], mx);
	}
	// cout << u << ' ' << dp[u][0][0] << ' ' << dp[u][0][1] << ' ' << dp[u][1][0] << ' ' << dp[u][1][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 << max(dp[1][0][0], dp[1][0][1]);
}

Compilation message (stderr)

beads.cpp: In function 'void dfs(int, int)':
beads.cpp:23:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i = 0; i < v.size(); i++) dp[u][0][0] += vals[i];
                 ~~^~~~~~~~~~
beads.cpp:27:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i = 0; i < v.size(); i++) mx = max(max(dp[v[i]][0][1], dp[v[i]][1][1] + w[i]) - vals[i], mx);
                 ~~^~~~~~~~~~
beads.cpp:30:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i = 0; i < v.size(); i++) {
                 ~~^~~~~~~~~~
beads.cpp:42:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i = 0; i < v.size(); i++) mx = max(dp[v[i]][0][0] + w[i] - vals[i], mx);
                 ~~^~~~~~~~~~
beads.cpp:47:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i = 0; i < v.size(); i++) mx = max(dp[v[i]][0][1] + w[i] - vals[i], mx);
                 ~~^~~~~~~~~~
beads.cpp:50:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i = 0; i < v.size(); i++) {
                 ~~^~~~~~~~~~

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