Submission #1085423

#	Time	Username	Problem	Language	Result	Execution time	Memory
1085423		guagua0407	Towns (IOI15_towns)	C++17	0 / 100	1 ms	348 KiB

towns

#include "towns.h"
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pii pair<int,int>
#define f first
#define s second
#define all(x) x.begin(),x.end()
#define _ ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);

int hubDistance(int N, int sub) {
	int n=N;
    vector<int> dis(n);
    for(int i=0;i<n;i++){
        dis[i]=getDistance(0,i);
    }
    int x=max_element(all(dis))-dis.begin();
    for(int i=0;i<n;i++){
        dis[i]=getDistance(x,i);
    }
    int y=max_element(all(dis))-dis.begin();
    vector<int> dis2(n);
    for(int i=0;i<n;i++){
        dis2[i]=getDistance(y,i);
    }
    vector<int> val1(n),val2(n);
    vector<int> vec;
    for(int i=0;i<n;i++){
        vec.push_back(dis[i]-(dis[i]+dis2[i]-dis[y])/2);
        val1[i]=dis[i]-(dis[i]+dis2[i]-dis[y])/2;
        val2[i]=(dis[i]+dis2[i]-dis[y])/2;
    }
    sort(all(vec));
    int R=dis[y];
    int ans=R;
    for(auto v:vec){
        ans=min(ans,max(v,R-v));
    }
    map<int,int> mp;
    for(auto v:vec){
        mp[v]++;
    }
    bool tf=false;
    int pre=0;
    for(auto v:mp){
        if(max(v.f,R-v.f)==ans){
            int mx=max({pre,v.s,n-pre-v.s});
            if(mx<=n/2){
                tf=true;
            }
        }
        pre+=v.s;
    }
    if(tf) return ans;
    pre=0;
    for(auto v:mp){
        if(max(v.f,R-v.f)==ans){
            if(v.s>n/2){
                vector<int> xs;
                for(int i=0;i<n;i++){
                    if(val1[i]==v.f){
                        xs.push_back(i);
                    }
                }
                mt19937 rng(time(NULL));
                uniform_int_distribution<int> gen(0,(int)xs.size()-1);
                tf=true;
                for(int t=0;t<5;t++){
                    int pos=gen(rng);
                    assert(pos>=0 and pos<(int)xs.size());
                    int cnt=0;
                    for(int i=0;i<(int)xs.size();i++){
                        if(i==pos){
                            cnt++;
                            continue;
                        }
                        int d=getDistance(xs[i],xs[pos]);
                        if(d!=val2[xs[i]]+val2[xs[pos]]) cnt++;
                    }
                    if(cnt>n/2){
                        tf=false;
                        break;
                    }
                }
            }
        }
        pre+=v.s;
    }
	return (tf?ans:-ans);
}

Compilation message (stderr)

towns.cpp: In function 'int hubDistance(int, int)':
towns.cpp:17:32: warning: conversion from '__gnu_cxx::__normal_iterator<int*, std::vector<int> >::difference_type' {aka 'long int'} to 'int' may change value [-Wconversion]
   17 |     int x=max_element(all(dis))-dis.begin();
      |           ~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~
towns.cpp:21:32: warning: conversion from '__gnu_cxx::__normal_iterator<int*, std::vector<int> >::difference_type' {aka 'long int'} to 'int' may change value [-Wconversion]
   21 |     int y=max_element(all(dis))-dis.begin();
      |           ~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~
towns.cpp:11:28: warning: unused parameter 'sub' [-Wunused-parameter]
   11 | int hubDistance(int N, int sub) {
      |                        ~~~~^~~

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