Submission #1028309

#	Time	Username	Problem	Language	Result	Execution time	Memory
1028309		huutuan	Towns (IOI15_towns)	C++14	25 / 100	15 ms	1188 KiB

towns

#include "towns.h"

#include <bits/stdc++.h>

using namespace std;

int dd[200][200], d1[200], d2[200];

mt19937 rng(69420);

int GetDistance(int u, int v){
   if (u==v) return 0;
   if (dd[u][v]) return dd[u][v];
   int tmp=getDistance(u, v);
   dd[u][v]=tmp; dd[v][u]=tmp;
   return tmp;
}

int hubDistance(int N, int sub) {
   memset(dd, 0, sizeof dd);
   memset(d1, 0, sizeof d1);
   memset(d2, 0, sizeof d2);
   int u=0, dis=0;
   for (int i=1; i<N; ++i){
      int d=GetDistance(0, i);
      if (d>dis){
         dis=d;
         u=i;
      }
   }
   dis=0;
   int v=u;
   for (int i=0; i<N; ++i) if (i!=u){
      int d=GetDistance(u, i);
      d1[i]=d;
      if (d>dis){
         dis=d;
         v=i;
      }
   }
   int ans=1e9;
   vector<pair<int, int>> vv;
   for (int i=0; i<N; ++i) if (i!=u && i!=v){
      d2[i]=GetDistance(v, i);
      int common=(d1[i]+d2[i]-dis)/2;
      int dl=d1[i]-common, dr=d2[i]-common;
      ans=min(ans, max(dl, dr));
      vv.emplace_back(dl, dr);
   }
   if (sub<=2) return ans;
   d1[u]=d2[v]=0;
   d1[v]=d2[u]=dis;
   sort(vv.begin(), vv.end());
   vv.resize(unique(vv.begin(), vv.end())-vv.begin());
   int cnt=0;
   for (auto &ii:vv) if (max(ii.first, ii.second)==ans) ++cnt;
   int mx=N/2;
   for (auto &ii:vv) if (max(ii.first, ii.second)==ans){
      int szl=0, szr=0;
      vector<pair<int, int>> child;
      for (int i=0; i<N; ++i){
         int common=(d1[i]+d2[i]-dis)/2;
         int dl=d1[i]-common, dr=d2[i]-common;
         if (dl<ii.first) ++szl;
         else if (dl>ii.first) ++szr;
         else child.emplace_back(i, 1);
      }
      if (szl>mx || szr>mx) continue;
      vector<pair<int, int>> dead;
      while ((int)child.size()>=2){
         if ((int)child.size()&1){
            dead.push_back(child.back());
            child.pop_back();
         }
         vector<pair<int, int>> new_child;
         for (int i=0; i<(int)child.size(); i+=2){
            int x=child[i].first, y=child[i+1].first;
            if ((d1[x]+d1[y]-ii.first*2-GetDistance(x, y))){
               new_child.emplace_back(x, child[i].second+child[i+1].second);
            }else{
               dead.push_back(child[i]);
               dead.push_back(child[i+1]);
            }
         }
         new_child.swap(child);
      }
      if (child.size()){
         int x=child[0].first, sz=child[0].second;
         for (auto &i:dead) if ((d1[x]+d1[i.first]-ii.first*2-GetDistance(x, i.first))) sz+=i.second;
         if (sz<=mx) return ans;
      }else return ans;
   }
   return -ans;
}

Compilation message (stderr)

towns.cpp: In function 'int hubDistance(int, int)':
towns.cpp:63:31: warning: unused variable 'dr' [-Wunused-variable]
   63 |          int dl=d1[i]-common, dr=d2[i]-common;
      |                               ^~

• Subtask 1: 13 / 13
• Subtask 2: 12 / 12
• Subtask 3: 0 / 13
• Subtask 4: 0 / 10
• Subtask 5: 0 / 13
• Subtask 6: 0 / 39