Submission #257174

#	Time	Username	Problem	Language	Result	Execution time	Memory
257174		eohomegrownapps	Towns (IOI15_towns)	C++14	25 / 100	21 ms	384 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;
    int hd = 0;
    //for (int x = 0; x<n; x++){
        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);
            }
        }
        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;
                vector<int> hubposs;
                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;
                        hubposs.clear();
                        hubposs.push_back(i);
                    } else if (rv==hubdist){
                        hubposs.push_back(i);
                    }
                }
                for (int hubind : hubposs){
                    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:89:52: 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:148:9: 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