Submission #1019649

#	Time	Username	Problem	Language	Result	Execution time	Memory
1019649		huutuan	Shortcut (IOI16_shortcut)	C++14	38 / 100	1018 ms	1372 KiB

shortcut

#include "shortcut.h"

#include <bits/stdc++.h>

using namespace std;

#define int long long

const int N=5000, inf=1e18;
int n, m, c, ll[N];
vector<pair<int, int>> g[N];
int tl, tr;
pair<int, int> f[N];

pair<int, int> dfs(int u, int p){
   pair<int, int> ans;
   int mx1=0, mx2=0;
   for (auto &e:g[u]){
      int v=e.first, w=e.second;
      if (v==p || (tl<=v && v<=tr)) continue;
      auto ff=dfs(v, u);
      ans.first=max(ans.first, ff.first);
      ans.second=max(ans.second, ff.second+w);
      if (mx1<ff.second+w) mx2=mx1, mx1=ff.second+w;
      else mx2=max(mx2, ff.second+w);
   }
   ans.first=max({ans.first, ans.second, mx1+mx2});
   return f[u]=ans;
}

int pf[N];

int calculate(int u, int v){
   tl=u, tr=v;
   pf[u]=0;
   for (int i=u; i<v; ++i) pf[i+1]=pf[i]+ll[i];
   int sum=pf[v]+c, ans=0;
   for (int i=u; i<=v; ++i){
      dfs(i, -1);
      ans=max(ans, f[i].first);
   }
   deque<int> dq;
   int mx=-inf;
   for (int i=u; i<=v; ++i){
      while (dq.size() && (pf[i]-pf[dq.front()])*2>sum){
         mx=max(mx, f[dq.front()].second+pf[dq.front()]);
         dq.pop_front();
      }
      if (dq.size()) ans=max(ans, f[i].second+f[dq.front()].second+pf[i]-pf[dq.front()]);
      if (mx!=-inf) ans=max(ans, f[i].second+sum-pf[i]+mx);
      while (dq.size() && f[dq.back()].second-pf[dq.back()]<f[i].second-pf[i]) dq.pop_back();
      dq.push_back(i);
   }
   return ans;
}

long long find_shortcut(int32_t _n, vector<int32_t> _l, vector<int32_t> _d, int32_t _c)
{
   n=_n, c=_c;
   for (int i=0; i<n-1; ++i) g[i].emplace_back(i+1, _l[i]), g[i+1].emplace_back(i, _l[i]), ll[i]=_l[i];
   m=n;
   for (int i=0; i<n; ++i) if (_d[i]){
      g[i].emplace_back(m, _d[i]);
      g[m].emplace_back(i, _d[i]);
      ++m;
   }
   int ans=inf;
   for (int i=0; i<n; ++i) for (int j=i+1; j<n; ++j){
      ans=min(ans, calculate(i, j));
   }
   return ans;
}

• Subtask 1: 9 / 9
• Subtask 2: 14 / 14
• Subtask 3: 8 / 8
• Subtask 4: 7 / 7
• Subtask 5: 0 / 33
• Subtask 6: 0 / 22
• Subtask 7: 0 / 4
• Subtask 8: 0 / 3