Submission #257184

#	Time	Username	Problem	Language	Result	Execution time	Memory
257184		eohomegrownapps	Towns (IOI15_towns)	C++14	48 / 100	29 ms	504 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 s){
    int hd = 0;
    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;
        }
    }

    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){
        //cout<<"hub: "<<hubind<<'\n';
        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;}
        if (s==4){
            if (nodesinhub.size()>n/2){exists=false;continue;}
            else {return hd;}
        }
        vector<bool> visited(n,false);
        int nodesleft = nodesinhub.size();
        for (int i : nodesinhub){
            if (visited[i]){continue;}
            if (nodesleft<=n/2){exists=true;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(sub);}

    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(int)':
towns.cpp:83:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             if (nodesinhub.size()>n/2){exists=false;continue;}
                 ~~~~~~~~~~~~~~~~~^~~~
towns.cpp:87:40: 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:143:9: warning: variable 'hubind' set but not used [-Wunused-but-set-variable]
     int hubind = -1;
         ^~~~~~

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