Submission #412698

#	Time	Username	Problem	Language	Result	Execution time	Memory
412698		LastRonin	Beads and wires (APIO14_beads)	C++14	28 / 100	1081 ms	12876 KiB

beads

#include <bits/stdc++.h>
#define speed ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
#define ll long long
#define pb push_back
#define mp make_pair
#define f first
#define s second
#define pill pair<ll, ll>
using namespace std;
const ll N = 5e5 + 10;
const ll big = 1e18;

ll n;
vector<pill> g[N];
ll dp[N][2], dp2[2][3], dp3[2][2];

ll dfs(ll v, ll p, ll z) {	
	dp[v][0] = dp[v][1] = 0;
	for(auto u : g[v]) {
		if(u.f != p)
			dfs(u.f, v, u.s);
	}
	dp2[0][0] = 0, dp2[0][1] = -big, dp2[0][2] = -big;
	for(auto u : g[v]) {	
		if(u.f == p)continue;
		dp2[1][0] = dp2[0][0] + max(dp[u.f][0], dp[u.f][1]);
		dp2[1][1] = max(dp2[0][1] + max(dp[u.f][0], dp[u.f][1]), dp2[0][0] + dp[u.f][0] + u.s);
		dp2[1][2] = max(dp2[0][2] + max(dp[u.f][0], dp[u.f][1]), dp2[0][1] + dp[u.f][0] + u.s);  
		dp2[0][0] = dp2[1][0];
		dp2[0][1] = dp2[1][1];
		dp2[0][2] = dp2[1][2];
	}
	dp[v][0] = dp2[0][0];
	dp[v][1] = dp2[0][1] + z;
	return dp2[0][2];
}

int main() {
	speed;
	cin >> n;
	for(ll i = 1, a, b, c; i < n; i++)
		cin >> a >> b >> c, g[a].pb(mp(b, c)), g[b].pb(mp(a, c));
	ll ans = 0;
	for(int i = 1; i <= n; i++)
		ans = max(ans, dfs(i, 0, 0));
	cout << ans;
}
/*
10
5 6 9
2 3 5
1 10 8
4 5 9
2 7 8
5 7 10
6 9 4
2 8 9
1 7 5


10
4 10 2
1 2 21
1 3 13
6 7 1
7 9 5
2 4 3
2 5 8
1 6 55
6 8 34

*/

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