Submission #433349

#	Time	Username	Problem	Language	Result	Execution time	Memory
433349		timmyfeng	Towns (IOI15_towns)	C++17	13 / 100	19 ms	344 KiB

towns

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

#include "towns.h"

const int N = 110;

int dist_0[N], dist_u[N], pos[N], color[N];

int hubDistance(int n, int subtask) {
    for (int i = 1; i < n; ++i) {
        dist_0[i] = getDistance(0, i);
    }

    int u = max_element(dist_0, dist_0 + n) - dist_0;
    dist_u[0] = dist_0[u];
    for (int i = 1; i < n; ++i) {
        dist_u[i] = u == i ? 0 : getDistance(u, i);
    }

    int v = max_element(dist_u, dist_u + n) - dist_u;
    pos[0] = (dist_0[u] - dist_0[v] + dist_u[v]) / 2;
    for (int i = 1; i < n; ++i) {
        pos[i] = min(pos[0], (dist_0[u] - dist_0[i] + dist_u[i]) / 2);
    }

    int ans = INT_MAX;
    map<int, vector<int>> groups;
    for (int i = 0; i < n; ++i) {
        ans = min(ans, max(pos[i], dist_u[v] - pos[i]));
        groups[pos[i]].push_back(i);
    }

    int left = 0, right = n;
    for (auto &[len, nodes] : groups) {
        right -= nodes.size();
        if (max(len, dist_u[v] - len) == ans) {
            if (max(left, right) <= n / 2) {
                int j = -1, balance = 0;
                for (auto i : nodes) {
                    if (balance == 0) {
                        j = i;
                    }

                    if (i == j || getDistance(i, j) < dist_u[i] + dist_u[j] - 2 * len) {
                        color[j] = i, ++balance;
                    } else {
                        color[j] = j, --balance;
                    }
                }

                int k = -1, count = 0;
                for (auto i : nodes) {
                    if (color[i] == i && getDistance(i, j) < dist_u[i] + dist_u[j] - 2 * len) {
                        k = i;
                    }
                    count += color[i] == k;
                }

                return count <= n / 2 ? ans : -ans;
            }
        }
        left += nodes.size();
    }

    return -ans;
}

Compilation message (stderr)

towns.cpp: In function 'int hubDistance(int, int)':
towns.cpp:15:45: warning: conversion from 'long int' to 'int' may change value [-Wconversion]
   15 |     int u = max_element(dist_0, dist_0 + n) - dist_0;
      |             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~
towns.cpp:21:45: warning: conversion from 'long int' to 'int' may change value [-Wconversion]
   21 |     int v = max_element(dist_u, dist_u + n) - dist_u;
      |             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~
towns.cpp:36:29: warning: conversion from 'std::vector<int>::size_type' {aka 'long unsigned int'} to 'int' may change value [-Wconversion]
   36 |         right -= nodes.size();
      |                             ^
towns.cpp:63:28: warning: conversion from 'std::vector<int>::size_type' {aka 'long unsigned int'} to 'int' may change value [-Wconversion]
   63 |         left += nodes.size();
      |                            ^
towns.cpp:10:28: warning: unused parameter 'subtask' [-Wunused-parameter]
   10 | int hubDistance(int n, int subtask) {
      |                        ~~~~^~~~~~~

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