Submission #257167

#	Time	Username	Problem	Language	Result	Execution time	Memory
257167		eohomegrownapps	Towns (IOI15_towns)	C++14	25 / 100	24 ms	512 KiB

towns

#include "towns.h"
#include <bits/stdc++.h>
using namespace std;

vector<vector<int>> distv;
int n;

int gd;

int dist(int a, int b){
    if (a==b){return 0;}
    if (a>b){
        swap(a,b);
    }
    if (distv[a][b]!=-1){
        return distv[a][b];
    } else {
        gd++;
        assert(gd<=(n*(n-1))/2);
        return distv[a][b]=getDistance(a,b);
    }
}

int grab(){
    int adist = -1;
    vector<int> aposs;
    for (int i = 0; i<n; i++){
        int ds = dist(0,i);
        if (adist<ds){
            adist=ds;
            aposs.clear();
            aposs.push_back(i);
        } else if (adist==ds){
            aposs.push_back(i);
        }
    }
    int hd = 0;
    for (int aind : aposs){
        int bdist = -1;
        vector<int> bposs;
        for (int i = 0; i<n; i++){
            int ds = dist(aind,i);
            if (bdist<ds){
                bdist=ds;
                bposs.clear();
                bposs.push_back(i);
            } else if (bdist==ds){
                bposs.push_back(i);
            }
        }
        for (int bind : bposs){
            bool exists = true;
            //from adist to aind
            //vector<int> diameter;
            int hubdist = 1e9;
            int hubind = -1;
            for (int i = 0; i<n; i++){
                if (i==aind||i==bind){continue;}
                int distfroma = dist(aind,i)-(dist(aind,i)+dist(bind,i)-dist(aind,bind))/2;
                int rv = max(distfroma,dist(aind,bind)-distfroma);
                if (rv<hubdist){
                    hubdist=rv;
                    hubind=i;
                }
            }
            hd=hubdist;
            int hubfroma = dist(aind,hubind)-(dist(aind,hubind)+dist(bind,hubind)-dist(aind,bind))/2;;
            vector<int> nodesinhub;
            int befcnt=0;
            int aftcnt=0;
            for (int i = 0; i<n; i++){
                int distfroma = dist(aind,i)-(dist(aind,i)+dist(bind,i)-dist(aind,bind))/2;
                if (distfroma<hubfroma){
                    befcnt++;
                } else if (distfroma==hubfroma){
                    nodesinhub.push_back(i);
                } else {
                    aftcnt++;
                }
            }
            //cout<<befcnt<<' '<<aftcnt<<' '<<nodesinhub.size()<<'\n';
            if (befcnt>n/2||aftcnt>n/2){exists=false;continue;}
            vector<bool> visited(n,false);
            int nodesleft = nodesinhub.size();
            for (int i : nodesinhub){
                if (visited[i]){continue;}
                if (nodesleft<=n/2){exists=false;break;}
                int nodesingrp = 1;
                visited[i]=true;
                for (int j : nodesinhub){
                    if (!visited[j]){
                        if (dist(i,j)<dist(aind,i)+dist(aind,j)-2*hubfroma){
                            nodesingrp++;
                            visited[j]=true;
                        }
                    }
                }
                //cout<<nodesingrp<<'\n';
                if (nodesingrp>n/2){exists=false;break;}
                nodesleft-=nodesingrp;
            }
            if (exists){
                return hd;
            }
        }
    }
    return -hd;
}

int hubDistance(int N, int sub) {
    gd=0;
    n=N;
    distv.assign(n,vector<int>(n,-1));
	
    if (sub>2){return grab();}

    int adist = -1;
    int aind = -1;
    for (int i = 0; i<n; i++){
        int ds = dist(1,i);
        if (adist<ds){
            adist=ds;
            aind=i;
        }
    }


    int bdist = -1;
    int bind = -1;
    for (int i = 0; i<n; i++){
        int ds = dist(aind,i);
        if (bdist<ds){
            bdist=ds;
            bind=i;
        }
    }

    //from adist to aind
    //vector<int> diameter;
    int hubdist = 1e9;
    int hubind = -1;
    for (int i = 0; i<n; i++){
        if (i==aind||i==bind){continue;}
        int distfroma = dist(aind,i)-(dist(aind,i)+dist(bind,i)-dist(aind,bind))/2;
        int rv = max(distfroma,dist(aind,bind)-distfroma);
        if (rv<hubdist){
            hubdist=rv;
            hubind=i;
        }
    }
    return hubdist;
}

Compilation message (stderr)

towns.cpp: In function 'int grab()':
towns.cpp:84:44: warning: conversion to 'int' from 'std::vector<int>::size_type {aka long unsigned int}' may alter its value [-Wconversion]
             int nodesleft = nodesinhub.size();
                             ~~~~~~~~~~~~~~~^~
towns.cpp: In function 'int hubDistance(int, int)':
towns.cpp:141:9: warning: variable 'hubind' set but not used [-Wunused-but-set-variable]
     int hubind = -1;
         ^~~~~~

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