Submission #1031005

#	Time	Username	Problem	Language	Result	Execution time	Memory
1031005		12345678	Towns (IOI15_towns)	C++17	100 / 100	21 ms	980 KiB

towns

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

using namespace std;

int hubDistance(int N, int sub) {
    vector<int> d[N];
	pair<int, int> mx={0, 0};
	int l=0, r, mn=INT_MAX;
	vector<int> dl(N), dr(N), dh(N);
	for (int i=1; i<N;i ++) dl[i]=getDistance(0, i), mx=max(mx, {dl[i], i});
	r=mx.second;
	dr[l]=dl[r];
	for (int i=0; i<N;i ++) if (i!=l&&i!=r) dr[i]=getDistance(r, i);
	int dist=dl[r];
	map<int, int> mp;
	map<int, vector<int>> mpd;
	for (int i=0; i<N; i++)
	{
		int x=dl[i], y=dr[i], h=(x+dist-y)/2;
        dh[i]=(x+y-dist)/2;
		if (mp.find(h)==mp.end()) mp[h]=dh[i];
		else mp[h]=max(mp[h], dh[i]);
		mpd[h].push_back(i);
	}	
	for (auto [x, a]:mp)
	{
		int mx=a;
		for (auto [y, b]:mp) mx=max(mx, abs(x-y)+b);
		mn=min(mn, mx); 
	}
	int sz=0, can=-1;
	for (auto [x, a]:mp)
	{
		int mx=a;
		for (auto [y, b]:mp) mx=max(mx, abs(x-y)+b);
		if (mn==mx) 
        {
            if (sz<=(N/2)&&(N-sz-(int)mpd[x].size()<=(N/2)))
            {
                if (((int)mpd[x].size())<=(N/2)) can=1;
                else
                {
                    int lst=0, freq=0;
                    for (auto idx:mpd[x])
                    {
                        if (freq==0)
                        {
                            freq++;
                            lst=idx;
                        }
                        else
                        {
                            if (getDistance(idx, lst)!=(dh[idx]+dh[lst])) d[lst].push_back(idx), freq++;
                            else freq--;
                        }
                    }
                    vector<int> vs(N);
                    int cnt=d[lst].size()+1;
                    vs[lst]=1;
                    for (auto idx:d[lst]) vs[idx]=1;
                    for (auto idx:mpd[x])
                    {
                        if (vs[idx]) continue;
                        if (getDistance(lst, idx)!=(dh[idx]+dh[lst]))
                        {
                            cnt+=1+d[idx].size();
                            vs[idx]=1;
                            for (auto y:d[idx]) vs[y]=1;
                        }
                        else
                        {
                            vs[idx]=1;
                            for (auto y:d[idx]) vs[y]=1;
                        }
                    }
                    if (cnt<=(N/2)) can=1;
                }
            }
        }
        sz+=mpd[x].size();
	}
	return mn*can;
}

Compilation message (stderr)

towns.cpp: In function 'int hubDistance(int, int)':
towns.cpp:28:7: warning: declaration of 'mx' shadows a previous local [-Wshadow]
   28 |   int mx=a;
      |       ^~
towns.cpp:8:17: note: shadowed declaration is here
    8 |  pair<int, int> mx={0, 0};
      |                 ^~
towns.cpp:35:7: warning: declaration of 'mx' shadows a previous local [-Wshadow]
   35 |   int mx=a;
      |       ^~
towns.cpp:8:17: note: shadowed declaration is here
    8 |  pair<int, int> mx={0, 0};
      |                 ^~
towns.cpp:59:42: warning: conversion from 'std::vector<int>::size_type' {aka 'long unsigned int'} to 'int' may change value [-Wconversion]
   59 |                     int cnt=d[lst].size()+1;
      |                             ~~~~~~~~~~~~~^~
towns.cpp:67:48: warning: conversion from 'std::vector<int>::size_type' {aka 'long unsigned int'} to 'int' may change value [-Wconversion]
   67 |                             cnt+=1+d[idx].size();
      |                                                ^
towns.cpp:81:25: warning: conversion from 'std::vector<int>::size_type' {aka 'long unsigned int'} to 'int' may change value [-Wconversion]
   81 |         sz+=mpd[x].size();
      |                         ^
towns.cpp:6:28: warning: unused parameter 'sub' [-Wunused-parameter]
    6 | int hubDistance(int N, int sub) {
      |                        ~~~~^~~

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