Submission #122470

#	Time	Username	Problem	Language	Result	Execution time	Memory
122470		youngyojun	Beads and wires (APIO14_beads)	C++11	28 / 100	1070 ms	5888 KiB

beads

#include <bits/stdc++.h>
#define eb emplace_back
#define sz(V) ((int)(V).size())
#define allv(V) ((V).begin()),((V).end())
#define upmax(a,b) (a)=max((a),(b))
#define INFLL (0x3f3f3f3f3f3f3f3fll)
using namespace std;
typedef long long ll;

const int MAXN = 200055;

ll D[MAXN], E[MAXN];

vector<int> G[MAXN];
int A[MAXN], B[MAXN], C[MAXN];

ll Ans;
int N;

void f(int i, int p, int pe) {
	D[i] = 0; E[i] = -INFLL;
	for(int e : G[i]) {
		int v = A[e]^B[e]^i;
		if(v == p) continue;
		f(v, i, C[e]);
		upmax(E[i], -max(D[v], E[v]) + D[v] + C[e]);
		D[i] += max(D[v], E[v]);
	}
	E[i] += D[i] + pe;
}

int main() {
	ios::sync_with_stdio(false);

	cin >> N;
	for(int i = 1; i < N; i++) {
		cin >> A[i] >> B[i] >> C[i];
		G[A[i]].eb(i);
		G[B[i]].eb(i);
	}

	vector<int> O;
	for(int i = 1; i <= N; i++) O.eb(i);
	random_shuffle(allv(O));

	for(int t = 0; t < N && t <= 4000; t++) {
		int i = O[t];
		ll ret = 0;
		for(int e : G[i]) {
			int v = A[e]^B[e]^i;
			f(v, i, C[e]);
			ret += max(D[v], E[v]);
		}
		upmax(Ans, ret);
	}

	cout << Ans << endl;
	return 0;
}

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