Submission #105100

#	Time	Username	Problem	Language	Result	Execution time	Memory
105100		Alexa2001	Towns (IOI15_towns)	C++17	51 / 100	36 ms	1024 KiB

towns

#include "towns.h"
#include <bits/stdc++.h>

using namespace std;

const int Nmax = 505;

int x, y;
int D0[Nmax], D1[Nmax], D2[Nmax], Up[Nmax], L[Nmax], R[Nmax];

map< int, vector<int> > gr;
map< pair<int,int> , int > mp;

int getDist(int x, int y)
{
    if(x == y) return 0;
    if(mp[{x,y}]) return mp[{x, y}];
    return mp[{x, y}] = mp[{y, x}] = getDistance(x, y);
}

void prepare(int n)
{
    int i;
    for(i=0; i<n; ++i) D0[i] = getDist(0, i);

    x = max_element(D0, D0+n) - D0;

    for(i=0; i<n; ++i) D1[i] = getDist(x, i);

    y = max_element(D1, D1+n) - D1;

    for(i=0; i<n; ++i) D2[i] = getDist(y, i);
}


bool check(vector<int> &v, int n)
{
    if(v.size() <= n/2) return 1;

    int candidat = v[0];
    int cnt = 0;

    for(auto it : v)
        if(getDist(candidat, it) == Up[candidat] + Up[it]) /// bucketuri diferite
        {
            if(!cnt) candidat = it, cnt = 1;
                else --cnt;
        }
        else ++cnt;

    cnt = v.size();
    for(auto it : v)
        if(getDist(candidat, it) == Up[candidat] + Up[it]) --cnt;

    return (cnt <= n/2);
}

int hubDistance(int n, int subtask)
{
    gr.clear();
    mp.clear();

    prepare(n);

    int total = D1[y];
    int ans = 2e9;
    int i;

    for(i=0; i<n; ++i)
    {
        Up[i] = D1[i] + D2[i] - total;
        assert(Up[i] % 2 == 0);
        Up[i] /= 2;

        L[i] = D1[i] - Up[i];
        R[i] = D2[i] - Up[i];

        assert(L[i] + R[i] == total);

        gr[L[i]].push_back(i);

        ans = min(ans, max(L[i], R[i]));
    }

    if(subtask <= 2) return ans;

    bool balanced = 0;
    int cnt1 = 0, cnt2 = n;

    for(auto &it : gr)
    {
        assert(it.second.size());

        cnt2 -= it.second.size();

        if(max(it.first, total - it.first) == ans && cnt1 <= n/2 && cnt2 <= n/2)
            balanced |= check(it.second, n);

        cnt1 += it.second.size();
    }

    return ans * (balanced ? 1 : -1);
}

Compilation message (stderr)

towns.cpp: In function 'int getDist(int, int)':
towns.cpp:14:25: warning: declaration of 'y' shadows a global declaration [-Wshadow]
 int getDist(int x, int y)
                         ^
towns.cpp:8:8: note: shadowed declaration is here
 int x, y;
        ^
towns.cpp:14:25: warning: declaration of 'x' shadows a global declaration [-Wshadow]
 int getDist(int x, int y)
                         ^
towns.cpp:8:5: note: shadowed declaration is here
 int x, y;
     ^
towns.cpp: In function 'void prepare(int)':
towns.cpp:26:31: warning: conversion to 'int' from 'long int' may alter its value [-Wconversion]
     x = max_element(D0, D0+n) - D0;
         ~~~~~~~~~~~~~~~~~~~~~~^~~~
towns.cpp:30:31: warning: conversion to 'int' from 'long int' may alter its value [-Wconversion]
     y = max_element(D1, D1+n) - D1;
         ~~~~~~~~~~~~~~~~~~~~~~^~~~
towns.cpp: In function 'bool check(std::vector<int>&, int)':
towns.cpp:38:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     if(v.size() <= n/2) return 1;
        ~~~~~~~~~^~~~~~
towns.cpp:51:17: warning: conversion to 'int' from 'std::vector<int>::size_type {aka long unsigned int}' may alter its value [-Wconversion]
     cnt = v.size();
           ~~~~~~^~
towns.cpp: In function 'int hubDistance(int, int)':
towns.cpp:94:32: warning: conversion to 'int' from 'std::vector<int>::size_type {aka long unsigned int}' may alter its value [-Wconversion]
         cnt2 -= it.second.size();
                                ^
towns.cpp:99:32: warning: conversion to 'int' from 'std::vector<int>::size_type {aka long unsigned int}' may alter its value [-Wconversion]
         cnt1 += it.second.size();
                                ^

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