Submission #670832

#	Time	Username	Problem	Language	Result	Execution time	Memory
670832		Arnch	Beads and wires (APIO14_beads)	C++17	57 / 100	211 ms	28568 KiB

beads

#include<bits/stdc++.h>
using namespace std;
 
#define Sz(x) (x).size()
#define All(x) (x).begin(), (x).end()
 
const int N = 1e5 + 10;
const long long INF = 1e18;
 
long long dp[N][4];
vector<pair<int, int> > adj[N];
 
void DFS(int x, int p = 0, int cnt = 0) {
    for(auto [j, t] : adj[x]) {
        if(j == p) continue;
        DFS(j, x, t);
    }
    if(Sz(adj[x]) == 1 && x != 1) {
        return;
    }
	vector<long long> vc;
	long long sum = 0;
	for(auto [j, t] : adj[x]) {
		if(j == p) continue;
		sum += dp[j][1];
	}
	// ba babash
	long long mx = -INF, mx2 = -INF;
	for(auto [j, t] : adj[x]) {
		if(j == p) continue;
		mx = max(mx, max(dp[j][2], dp[j][3]) + t - dp[j][1]);
		mx2 = max(mx2, dp[j][3] + t - dp[j][1]);
	}
	dp[x][0] = max(dp[x][0], sum + mx + cnt);
	dp[x][1] = max(dp[x][1], sum + mx2 + cnt);
	// ba bachash
	long long ind = 0; mx = -INF;
	for(auto [j, t] : adj[x]) {
		if(j == p) continue;
		if((dp[j][2] - dp[j][1] + t >= mx) || ind == 0) {
			mx = dp[j][2] - dp[j][1] + t;
			ind = j;
		}
	}
	vc.clear();
	for(auto [j, t] : adj[x]) {
		if(j == ind || j == p) continue;
		vc.push_back(dp[j][3] + t - dp[j][1]);
	}
	sort(All(vc), greater<long long>());
	if(Sz(vc) > 0) {
		dp[x][0] = max(dp[x][0], sum + mx + vc[0]);
		dp[x][2] = max(dp[x][2], sum + mx + vc[0]);
	}
	if(Sz(vc) > 1) {
		dp[x][0] = max(dp[x][0], sum + vc[1] + vc[0]);
		dp[x][2] = max(dp[x][2], sum + vc[1] + vc[0]);
	}
	ind = 0; mx = -INF;
	for(auto [j, t] : adj[x]) {
		if(j == p) continue;
		if((dp[j][3] - dp[j][1] + t >= mx) || ind == 0) {
			mx = dp[j][3] - dp[j][1] + t;
			ind = j;
		}
	}
	vc.clear();
	for(auto [j, t] : adj[x]) {
		if(j == ind || j == p) continue;
		vc.push_back(dp[j][2] + t - dp[j][1]);
	}
	sort(All(vc), greater<long long>());
	if(Sz(vc) > 0) {
		dp[x][0] = max(dp[x][0], sum + mx + vc[0]);
		dp[x][2] = max(dp[x][2], sum + mx + vc[0]);
	}
	// hich kodom
	mx = -INF;
	for(auto [j, t] : adj[x]) {
		if(j == p) continue;
		mx = max(mx, dp[j][0] - dp[j][1]);
	}
	for(int i = 0; i < 4; i++) dp[x][i] = max(dp[x][i], sum);
	dp[x][0] = max(dp[x][0], sum + mx);
	dp[x][2] = max(dp[x][2], sum + mx);
}
 
int main() {
    int n; cin >>n;
    for(int i = 0; i < n - 1; i++) {
        int u, v, c; cin >>u >>v >>c;
        adj[u].push_back({v, c}), adj[v].push_back({u, c});
    }
 
    DFS(1);

	/*for(int i = 1; i <= n; i++) {
		cout<<"^^" <<i <<' ' <<dp[i][0] <<' ' <<dp[i][1] <<' ' <<dp[i][2] <<' ' <<dp[i][3] <<endl;
	}*/

	cout<<dp[1][2] <<endl;
}

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