Submission #257070

#	Time	Username	Problem	Language	Result	Execution time	Memory
257070		eohomegrownapps	Towns (IOI15_towns)	C++14	25 / 100	23 ms	496 KiB

towns

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

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

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 {
        return distv[a][b]=getDistance(a,b);
    }
}

int hubDistance(int N, int sub) {
    n=N;
    distv.assign(n,vector<int>(n,-1));
	
    int adist = -1;
    int aind = -1;
    for (int i = 0; i<n; i++){
        int ds = dist(0,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;
        }
    }
    if (sub<=2){return hubdist;}
	int hubfroma = dist(aind,hubind)-(dist(aind,hubind)+dist(bind,hubind)-dist(aind,bind))/2;
    
    vector<int> nodesinhub;
    int befcnt;
    int aftcnt;
    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++;
        }
    }
    if (befcnt>n/2||aftcnt>n/2){return -hubdist;}
    vector<bool> visited(n);
    int nodesleft = nodesinhub.size();
    for (int i : nodesinhub){
        if (visited[i]){continue;}
        if (nodesleft<=n/2){break;}
        int nodesingrp = 1;
        visited[i]=true;
        for (int j : nodesinhub){
            if (!visited[j]){
                if (dist(i,j)<dist(aind,i)-dist(aind,hubind)+dist(bind,i)-dist(bind,hubind)){
                    nodesingrp++;
                }
            }
        }
        if (nodesingrp>n/2){return -hubdist;}
        nodesleft-=nodesingrp;
    }
    return hubdist;
}

Compilation message (stderr)

towns.cpp: In function 'int hubDistance(int, int)':
towns.cpp:76:36: 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:74:19: warning: 'aftcnt' may be used uninitialized in this function [-Wmaybe-uninitialized]
     if (befcnt>n/2||aftcnt>n/2){return -hubdist;}
         ~~~~~~~~~~^~~~~~~~~~~~
towns.cpp:74:5: warning: 'befcnt' may be used uninitialized in this function [-Wmaybe-uninitialized]
     if (befcnt>n/2||aftcnt>n/2){return -hubdist;}
     ^~

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