Submission #795484

#	Time	Username	Problem	Language	Result	Execution time	Memory
795484		Josia	Towns (IOI15_towns)	C++17	0 / 100	40 ms	440 KiB

towns

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


map<pair<int, int>, int> queries;
int getd(int a, int b) {
	if (a>b) swap(a,b);
	if (a==b) return 0;

	if (queries.count({a,b})) return queries[{a,b}];

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






struct UF {
	map<int, int> chefs;

	UF(vector<int> elems) {
		for (int i: elems) chefs[i] = i;
	}

	int find(int x) {
		if (chefs[x] == x) return x;
		chefs[x] = find(chefs[x]);
		return chefs[x];
	}

	void unite (int a, int b) {
		a = find(a);
		b = find(b);
		chefs[a] = b;
	}
};




int hubDistance(int N, int sub) {
	int d1=0, v1 = 0;
	for (int i = 1; i<N; i++) {
		int d = getd(0, i);
		if (d>d1) {
			d1 = d;
			v1 = i;
		}
	}

	vector<int> dists1(N);

	int d2=0, v2=v1;
	for (int i = 0; i<N; i++) {
		int d = getd(v1, i);
		dists1[i] = d;
		if (d>d2) {
			d2 = d;
			v2 = i;
		}
	}

	vector<int> dists2(N);
	for (int i = 0; i<N; i++) {
		int d = getd(v2, i);
		dists2[i] = d;
	}


	map<int, vector<int>> joinedDiam;


	int R = 1e9;
	for (int i = 0; i<N; i++) {
		int rem = (dists1[i]+dists2[i]-d2)/2;

		joinedDiam[dists1[i]-rem].push_back(i);

		R = min(R, max(dists1[i]-rem, dists2[i]-rem));
	}

	vector<int> possHub;

	for (int i = 0; i<N; i++) {
		int rem = (dists1[i]+dists2[i]-d2)/2;
		if (max(dists1[i]-rem, dists2[i]-rem) == R) possHub.push_back(dists1[i]-rem);
	}

	int mult = -1;
	for (int hub: possHub) {
		int h1=0, h2=0;
		bool poss = 1;
		for (auto i: joinedDiam) {
			if (i.first < hub) h1+=i.second.size();
			if (i.first > hub) h2+=i.second.size();
			if (i.first == hub) {
				if ((int)i.second.size() > N/2) {

					UF u(i.second);

					for (int a: i.second) {
						for (int b: i.second) {
							// cerr << a << " " << b << "\n";
							if (a >= b) continue;

							int da = (dists1[a]+dists2[a]-d2)/2;
							int db = (dists1[b]+dists2[b]-d2)/2;

							// cerr << a << " " << b << "\n";
							int d = getd(a,b);
							if (d != da+db) u.unite(a,b);
						}
					}

					map<int, int> count;
					for (auto j: u.chefs) count[j.second]++;
					int Max = 0;
					for (auto j: count) Max = max(Max, j.second);

					if (Max > N/2) poss = 0;
				}
			}
		}
		if (h1 > N/2 || h2 > N/2) poss = 0;

		if (poss) mult = 1;
	}

	// cerr << R << "\n";
	return R*mult;
}

Compilation message (stderr)

towns.cpp: In function 'int hubDistance(int, int)':
towns.cpp:97:41: warning: conversion from 'std::vector<int>::size_type' {aka 'long unsigned int'} to 'int' may change value [-Wconversion]
   97 |    if (i.first < hub) h1+=i.second.size();
      |                                         ^
towns.cpp:98:41: warning: conversion from 'std::vector<int>::size_type' {aka 'long unsigned int'} to 'int' may change value [-Wconversion]
   98 |    if (i.first > hub) h2+=i.second.size();
      |                                         ^
towns.cpp:44:28: warning: unused parameter 'sub' [-Wunused-parameter]
   44 | int hubDistance(int N, int sub) {
      |                        ~~~~^~~

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