Submission #383892

#	Time	Username	Problem	Language	Result	Execution time	Memory
383892		LucaDantas	Towns (IOI15_towns)	C++17	25 / 100	26 ms	876 KiB

towns

#include "towns.h"
#include <cstring>
#include <cstdio>
#include <algorithm>
#include <cassert>
#include <vector>
#include <map>
 
constexpr int maxn = 300;
 
int dp[maxn][maxn], c[maxn];

std::map<int, std::vector<int>> filhos;
 
int get(int i, int j) {
	if(i > j) std::swap(i, j);
	return dp[i][j] != -1 ? dp[i][j] : dp[i][j] = getDistance(i, j);
}

struct DSU
{
	int pai[maxn], peso[maxn];
	void init() { for(int i = 0; i < maxn; i++) pai[i] = i, peso[i] = 1; }
	int find(int x) { return pai[x] == x?x:pai[x]=find(pai[x]); }
	void join(int a, int b) {
		a = find(a), b = find(b);
		if(a == b) return;
		if(peso[a] < peso[b])
			std::swap(a, b);
		pai[b] = a;
		peso[a] += peso[b];
	}
	int sz(int x) { return peso[find(x)]; }
} dsu;

int max(int a, int b) { return a > b ? a : b; }
int min(int a, int b) { return a < b ? a : b; }
 
int hubDistance(int N, int sub) {
	memset(dp, -1, sizeof dp);
	memset(c, 0, sizeof c);
	filhos.clear();
	dsu.init();
	int a = 0, b = 0, dist = 0;
	for(int i = 0; i < 2; i++) {
		for(int j = 0; j < N; j++) {
			if(a != j) {
				int v = get(a, j);
				if(v > dist) b = j, dist = v;
			}
		}
		if(!i) std::swap(a, b);
	}
	b = 0;
	int R = 0x3f3f3f3f;
	for(int i = 0; i < N; i++) {
		if(i == a || i == b) continue;
		int d1 = get(a, i), d2 = get(b, i);
		c[i] = (d1 + d2 - get(a, b)) >> 1;
		R = min(R, max(d1 - c[i], dist - d1 + c[i]));
		filhos[d1-c[i]].push_back(i);
	}

	std::vector<int> lista, bucket;

	int sz = 0; bool ok = 0;
	for(auto it : filhos) {
		if(it.first != R && it.first != dist - R) {
			sz += (int)(it.second).size();
			continue;
		}
		if(sz <= (N >> 1) && N - sz - (int)(it.second).size() <= (N >> 1)) ok = 1;
		else continue;
		std::vector<int> v = (it.second);
		int n = (int)v.size();
		if(n <= (N >> 1)) { sz += n; continue; }
		for(int i = 0; i < n; i++) {
			if(!lista.size()) lista.push_back(v[i]);
			else if(get(v[i], lista.back()) != c[v[i]] + c[lista.back()])
				bucket.push_back(v[i]);
			else {
				lista.push_back(v[i]);
				if(bucket.size()) lista.push_back(bucket.back()),
				bucket.pop_back();
			}
		}
		// puts("lista");
		// for(int x : lista)
		// 	printf("%d\n", x);
		// puts("bucket");
		// for(int x : bucket)
		// 	printf("%d\n", x);
		int pivo = lista.back(); lista.pop_back();
		while(bucket.size() && lista.size()) {
			if(get(pivo, lista.back()) != c[lista.back()] + c[pivo])
				lista.pop_back(), bucket.pop_back();
			else {
				lista.pop_back(); if(lista.size()) lista.pop_back();
			}
		}
		// puts("bucket");
		// for(int x : bucket)
		// 	printf("%d\n", x);
		ok &= bucket.size() < N - n;
		if(ok) return R;
		sz += n;
	}

	return -R;
}

Compilation message (stderr)

towns.cpp: In function 'int hubDistance(int, int)':
towns.cpp:104:23: warning: comparison of integer expressions of different signedness: 'std::vector<int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
  104 |   ok &= bucket.size() < N - n;
      |         ~~~~~~~~~~~~~~^~~~~~~
towns.cpp:39:28: warning: unused parameter 'sub' [-Wunused-parameter]
   39 | int hubDistance(int N, int sub) {
      |                        ~~~~^~~

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