Submission #586728

#	Time	Username	Problem	Language	Result	Execution time	Memory
586728		InternetPerson10	Towns (IOI15_towns)	C++17	25 / 100	17 ms	372 KiB

towns

#include "towns.h"
#include <bits/stdc++.h>
typedef long long ll;

using namespace std;

map<pair<int, int>, int> distances;

int getDist(int i, int j) {
    if(i == j) return 0;
    if(i > j) swap(i, j);
    if(distances.count({i, j})) {
        return distances[make_pair(i, j)];
    }
    return distances[make_pair(i, j)] = getDistance(i, j);
}

vector<int> dists;
map<ll, int> xs;

int hubDistance(int n, int sub) {
    ll ans = 2e10;
    distances.clear();
    dists.clear();
    xs.clear();
    dists.resize(n);
    int ma = -1, best = -1;
    for(int i = 0; i < n; i++) {
        dists[i] = getDist(0, i);
        if(ma < dists[i]) {
            ma = dists[i];
            best = i;
        }
    }
    int x = best;
    ma = -1, best = -1;
    for(int i = 0; i < n; i++) {
        dists[i] = getDist(x, i);
        if(ma < dists[i]) {
            ma = dists[i];
            best = i;
        }
    }
    int y = best;
    ll c = ma;
    for(int i = 0; i < n; i++) {
        if(i == x || i == y) continue;
        int a = getDist(x, i);
        int b = getDist(y, i);
        ans = min(ans, max(a + c - b, b + c - a));
        if(!xs.count(a+c-b)) {
            xs[a+c-b] = 1;
        }
        else xs[a+c-b]++;
    }
    ll cand = -1;
    int sum = 0;
    for(auto p : xs) {
        bool ok = true;
        ok &= (sum <= n/2);
        sum += p.second;
        if(sub == 4) ok &= (p.second <= n/2);
        ok &= (sum >= n - n/2);
        if(ok) cand = p.first;
    }
    if(sub == 4) {
        if(cand == -1) return -ans/2;
        return ans/2;
    }
    return ans/2;
}

Compilation message (stderr)

towns.cpp: In function 'int hubDistance(int, int)':
towns.cpp:67:35: warning: conversion from 'll' {aka 'long long int'} to 'int' may change value [-Wconversion]
   67 |         if(cand == -1) return -ans/2;
      |                               ~~~~^~
towns.cpp:68:19: warning: conversion from 'll' {aka 'long long int'} to 'int' may change value [-Wconversion]
   68 |         return ans/2;
      |                ~~~^~
towns.cpp:70:15: warning: conversion from 'll' {aka 'long long int'} to 'int' may change value [-Wconversion]
   70 |     return ans/2;
      |            ~~~^~

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