Submission #288517

#	Time	Username	Problem	Language	Result	Execution time	Memory
288517		Saboon	Towns (IOI15_towns)	C++17	13 / 100	22 ms	504 KiB

towns

#include "towns.h"
#include<bits/stdc++.h>
using namespace std;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const int inf = 2e8 + 10;
int n, d[110][110];
int cnt[110];

int Dis(int v, int u){
	if (v == u or d[v][u] > 0)
		return d[v][u];
	return d[v][u] = d[u][v] = getDistance(v,u);
}

int getDis(int v, int u, int w){
	return (Dis(v,u)+Dis(v,w)-Dis(u,w))/2;
}

int hubDistance(int N, int sub){
	memset(d, 0, sizeof d);
	n = N;
	int Q1 = 0, Q2 = 0;
	for (int i = 1; i < n; i++)
		if (Dis(0,i) > Dis(0,Q1))
			Q1 = i;
	for (int i = 1; i < n; i++)
		if (Dis(Q1,i) > Dis(Q1,Q2))
			Q2 = i;
	int R = inf;
	vector<int> a;
	for (int v = 0; v < n; v++){
		if (v == Q1 or v == Q2)
			continue;
		int A = getDis(Q1, Q2, v), B = getDis(Q2, Q1, v);
		a.push_back(A);
		R = min(R,max(A,B));
	}
	sort(a.begin(), a.end());
	a.resize(unique(a.begin(),a.end())-a.begin());
	int m = 1;
	for (auto it : a){
		int now = 0;
		vector<int> b;
		for (int v = 0; v < n; v++){
			if (v == Q1 or v == Q2)
				continue;
			if (getDis(Q1, Q2, v) == it)
				now ++, b.push_back(v);
		}
		int t = max(it,Dis(Q1,Q2)-it);
		if (t != R or m > n/2 or (n-m-now) > n/2){
			m += now;
			continue;
		}
		if (now <= n/2)
			return R;
		memset(cnt, 0, sizeof cnt);
		vector<int> nom;
		shuffle(b.begin(), b.end(), rng);
		nom.push_back(b[0]);
		cnt[b[0]] ++;
		int Constant = 8, check = -1;
		for (int i = 1; i < now; i++){
			if (i <= Constant){
				bool found = 0;
				for (auto j : nom)
					if (getDis(Q1,j,b[i]) > it)
						cnt[j] ++, found = 1;
				if (!found)
					nom.push_back(b[i]), cnt[b[i]] ++;
				if (i == Constant){
					sort(nom.begin(), nom.end(), [](int x, int y){return cnt[x] > cnt[y];});
					check = nom[0];
				}
			}
			else{
				if (getDis(Q1,check,b[i]) == it)
					cnt[check] ++;
			}
		}
		if (cnt[check] <= n/2)
			return R;
		m += now;
	}
	return -R;
}

Compilation message (stderr)

towns.cpp: In function 'int hubDistance(int, int)':
towns.cpp:19:28: warning: unused parameter 'sub' [-Wunused-parameter]
   19 | int hubDistance(int N, int sub){
      |                        ~~~~^~~

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