Submission #675488

#	Time	Username	Problem	Language	Result	Execution time	Memory
675488		AmirAli_H1	Beads and wires (APIO14_beads)	C++17	100 / 100	195 ms	40848 KiB

beads

// In the name of Allah

#include <bits/stdc++.h>
using namespace std;

typedef long long int	ll;
typedef long double	ld;
typedef pair<int, int>	pii;
typedef pair<ll, ll>	pll;

#define all(x)		(x).begin(),(x).end()
#define len(x)		((ll) (x).size())
#define F		first
#define S		second
#define pb		push_back
#define sep             ' '
#define endl            '\n'
#define Mp		make_pair
#define debug(x)	cerr << #x << ": " <<  x << endl;
#define kill(x)		cout << x << '\n', exit(0);
#define set_dec(x)	cout << fixed << setprecision(x);
#define file_io(x,y)	freopen(x, "r", stdin); freopen(y, "w", stdout);

int n;
const int maxn = 2e5 + 5;
const ll oo = 1e14;
vector<pll> adj[maxn];
ll dp[maxn][2][2];
bool mark[maxn];

void dfs(int v, ll x = -1) {
	mark[v] = 1;
	ll res = 0;
	vector<pll> ls1, ls2, ls3;
	for (auto f : adj[v]) {
		auto [u, w] = f;
		if (!mark[u]) {
			dfs(u, w);
			
			res += dp[u][1][0];
			
			ls1.pb(Mp(w + dp[u][0][0] - dp[u][1][0], u));
			ls2.pb(Mp(w + dp[u][0][1] - dp[u][1][0], u));
			ls3.pb(Mp(dp[u][1][1] - dp[u][1][0], u));
		}
	}
	
	sort(all(ls1), greater<pll>()); sort(all(ls2), greater<pll>()); sort(all(ls3), greater<pll>());
	
	if (x == -1 || len(ls1) < 1) {
		dp[v][1][0] = -oo;
		dp[v][1][1] = -oo;
	}
	else {
		dp[v][1][0] = max(-oo, res + x + ls1[0].F);
		dp[v][1][1] = max(-oo, res + x + ls2[0].F);
	}
	
	dp[v][0][0] = res;
	if (len(ls3) < 1) dp[v][0][1] = -oo;
	else dp[v][0][1] = max(-oo, res + ls3[0].F);
	
	if (len(ls1) >= 2) {
		dp[v][0][1] = max(dp[v][0][1], res + ls1[0].F + ls1[1].F);
		if (ls1[0].S != ls2[0].S) {
			dp[v][0][1] = max(dp[v][0][1], res + ls1[0].F + ls2[0].F);
		}
		else {
			dp[v][0][1] = max(dp[v][0][1], res + ls1[0].F + ls2[1].F);
			dp[v][0][1] = max(dp[v][0][1], res + ls1[1].F + ls2[0].F);
		}
	}
	
	dp[v][1][0] = max(dp[v][1][0], dp[v][0][0]);
	dp[v][1][1] = max(dp[v][1][1], dp[v][0][1]);
	
	ls1.clear(); ls1.shrink_to_fit();
	ls2.clear(); ls2.shrink_to_fit();
	ls3.clear(); ls3.shrink_to_fit();
}

int main() {
	ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
	
	cin >> n;
	for (int i = 0; i < n - 1; i++) {
		int u, v; ll w;
		cin >> u >> v >> w; u--; v--;
		adj[u].pb(Mp(v, w)); adj[v].pb(Mp(u, w));
	}
	
	dfs(0);
	
	cout << max(dp[0][0][0], dp[0][0][1]) << endl;
	
	return 0;
}

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