Submission #957999

#	Time	Username	Problem	Language	Result	Execution time	Memory
957999		vjudge1	Beads and wires (APIO14_beads)	C++14	100 / 100	205 ms	64324 KiB

beads

#include<bits/stdc++.h>

using namespace std;

#define int long long

const int N=2e5+10, inf=1e18;
int f[N][2][3][3];
vector<pair<int, int>> g[N];

void dfs(int u, int p){
   int wpar=0;
   for (int i=0; i<(int)g[u].size(); ++i) if (g[u][i].first==p){
      wpar=g[u][i].second;
      g[u].erase(g[u].begin()+i);
      break;
   }
   for (auto &e:g[u]) dfs(e.first, u);
   vector<int> sum(3);
   for (auto &e:g[u]){
      int v=e.first;
      for (int i=0; i<3; ++i) sum[i]+=max(f[v][0][i][0], f[v][1][i][1]);
   }
   f[u][0][0][0]=sum[0];
   if ((int)g[u].size()>=2){
      vector<vector<pair<int, int>>> diff(3);
      for (auto &e:g[u]){
         int v=e.first, w=e.second;
         for (int i=0; i<3; ++i) diff[i].emplace_back(f[v][0][1][i]+w-max(f[v][0][1][0], f[v][1][1][1]), v);
      }
      for (int i=0; i<3; ++i) sort(diff[i].rbegin(), diff[i].rend());
      int mxdiff=-inf;
      for (int c2=0; c2<3; ++c2){
         int c1=0;
         for (int i1=0; i1<2; ++i1) for (int i2=0; i2<2; ++i2) if (diff[c1][i1].second!=diff[c2][i2].second){
            mxdiff=max(mxdiff, diff[c1][i1].first+diff[c2][i2].first);
         }
      }
      f[u][0][0][1]=sum[1]+mxdiff;
   }
   if (g[u].size()){
      vector<int> diff;
      for (auto &e:g[u]){
         int v=e.first;
         diff.push_back(max({f[v][0][2][1], f[v][0][2][2], f[v][1][2][1]})-max(f[v][0][0][0], f[v][1][0][1]));
      }
      sort(diff.rbegin(), diff.rend());
      f[u][0][0][2]=sum[0]+diff[0];
   }
   if (p && g[u].size()){
      vector<int> diff;
      for (auto &e:g[u]){
         int v=e.first, w=e.second;
         diff.push_back(f[v][0][1][0]+w+wpar-max(f[v][0][1][0], f[v][1][1][1]));
      }
      sort(diff.rbegin(), diff.rend());
      f[u][1][0][1]=sum[1]+diff[0];
   }
   if (p && g[u].size()){
      vector<int> diff;
      for (auto &e:g[u]){
         int v=e.first, w=e.second;
         diff.push_back(max(f[v][0][1][1], f[v][0][1][2])+w+wpar-max(f[v][0][1][0], f[v][1][1][1]));
      }
      sort(diff.rbegin(), diff.rend());
      f[u][1][2][1]=sum[1]+diff[0];
   }
   for (int i=0; i<2; ++i) for (int j=0; j<3; ++j){
      f[u][i][1][j]=max(f[u][i][1][j], f[u][i][0][j]);
      f[u][i][2][j]=max(f[u][i][2][j], f[u][i][0][j]);
   }
}

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], f[1][0][0][2]});
   return 0;
}

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