Submission #957397

#	Time	Username	Problem	Language	Result	Execution time	Memory
957397		vjudge1	Beads and wires (APIO14_beads)	C++14	13 / 100	3 ms	6748 KiB

beads

#include<bits/stdc++.h>

using namespace std;

#define int long long

const int N=2e5+10, inf=1e18;
int f[N][2][2][2];
vector<pair<int, int>> g[N];

void dfs(int u, int p){
   for (int i=0; i<8; ++i) f[u][!!(i&1)][!!(i&2)][!!(i&4)]=-inf;
   for (auto &e:g[u]) if (e.first!=p) dfs(e.first, u);
   vector<int> sum(2);
   for (int cu=0; cu<=1; ++cu){
      for (auto &e:g[u]) if (e.first!=p){
         int mx=-inf;
         for (int t=0; t<=1; ++t) for (int cv=0; cv<=(!cu || t); ++cv) mx=max(mx, f[e.first][t][cu][cv]);
         sum[cu]+=mx;
      }
   }
   f[u][0][0][0]=sum[0];
   vector<vector<pair<int, int>>> tmp(2);
   for (auto &e:g[u]) if (e.first!=p){
      int mx1=-inf;
      for (int t=0; t<=1; ++t) for (int cv=0; cv<=t; ++cv) mx1=max(mx1, f[e.first][t][1][cv]);
      for (int cv=0; cv<=1; ++cv){
         tmp[cv].emplace_back(f[e.first][0][1][cv]+e.second-mx1, e.first);
      }
   }
   sort(tmp[0].rbegin(), tmp[0].rend());
   sort(tmp[1].rbegin(), tmp[1].rend());
   if ((int)tmp[0].size()>=2){
      for (int t0=0; t0<=1; ++t0) for (int t1=t0; t1<=1; ++t1) if (!(t0&t1)){
         if (tmp[t0][0].second!=tmp[t1][0].second) f[u][0][0][1]=max(f[u][0][0][1], sum[1]+tmp[t0][0].first+tmp[t1][0].first);
         if (tmp[t0][0].second!=tmp[t1][1].second) f[u][0][0][1]=max(f[u][0][0][1], sum[1]+tmp[t0][0].first+tmp[t1][1].first);
         if (tmp[t0][1].second!=tmp[t1][0].second) f[u][0][0][1]=max(f[u][0][0][1], sum[1]+tmp[t0][1].first+tmp[t1][0].first);
      }
   }
   f[u][0][1][0]=f[u][0][0][0];
   f[u][0][1][1]=f[u][0][0][1];
   if (p){
      int wpar=0;
      for (auto &e:g[p]) if (e.first==u) wpar=e.second;
      tmp[0].clear(); tmp[1].clear();
      for (auto &e:g[u]) if (e.first!=p){
         int mx1=-inf;
         for (int t=0; t<=1; ++t) for (int cv=0; cv<=t; ++cv) mx1=max(mx1, f[e.first][t][1][cv]);
         for (int cv=0; cv<=1; ++cv){
            tmp[cv].emplace_back(f[e.first][0][1][cv]+e.second+wpar-mx1, e.first);
         }
      }
      sort(tmp[0].rbegin(), tmp[0].rend());
      sort(tmp[1].rbegin(), tmp[1].rend());
      if (tmp[0].size()){
         f[u][1][0][1]=sum[1]+max(tmp[0][0].first, tmp[1][0].first);
         f[u][1][1][1]=sum[1]+tmp[0][0].first;
      }
   }
}

int32_t main(){
   ios_base::sync_with_stdio(false);
   cin.tie(nullptr);
   int n;
   cin >> n;
   for (int i=1; i<n; ++i){
      int u, v, w; cin >> u >> v >> w;
      g[u].emplace_back(v, w);
      g[v].emplace_back(u, w);
   }
   dfs(1, 0);
   cout << max(f[1][0][0][0], f[1][0][0][1]);
   return 0;
}

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