Submission #1019129

#	Time	Username	Problem	Language	Result	Execution time	Memory
1019129		parsadox2	Towns (IOI15_towns)	C++17	100 / 100	12 ms	1116 KiB

towns

#include "towns.h"
#include <bits/stdc++.h>
 
#define F first
#define S second
 
using namespace std;
 
const int N = 1e2 + 20;
int n , dis[N][N] , r[N] , L[N] , R[N] , C[N];
bool marked[N];
 
bool Solve(int D)
{
	int lef = 0 , rig = 0 , mid = 0;
	for(int x = 0 ; x < n ; x++)
	{
		marked[x] = false;
		C[x] = 1;
	}
	int mx = -1 , cnt = 0;
	for(int x = 0 ; x < n ; x++)
	{
		if(L[x] < D)
		{
			marked[x] = true;
			lef++;
		}
		else if(L[x] > D)
		{
			marked[x] = true;
			rig++;
		}
		else
		{
			if(cnt == 0)
			{
				cnt = 1;
				mx = x;
				continue;
			}
			else
			{
				dis[mx][x] = dis[x][mx] = getDistance(x , mx);
				if(dis[x][mx] != r[x] + r[mx])
				{
					C[mx]++;
					marked[x] = true;
					cnt++;
				}
				else
					cnt--;
			}
		}
	}
	mid = C[mx];
	for(int x = 0 ; x < n ; x++)  if(L[x] == D && x != mx && !marked[x])
	{
		dis[x][mx] = dis[mx][x] = getDistance(x , mx);
		if(dis[x][mx] != r[x] + r[mx])
			mid += C[x];
	}
	return (lef <= n / 2 && rig <= n/2 && mid <= n / 2);
}

int hubDistance(int nn , int sub) {
	n = nn;
	pair <int , int> D = make_pair(0 , 1);
	for(int i = 1 ; i < n ; i++)
	{
		dis[0][i] = dis[i][0] = getDistance(0 , i);
		if(dis[0][i] > dis[D.F][D.S])
			D = make_pair(0 , i);
	}
	int diam = 0;
	for(int i = 0 ; i < n ; i++)  if(i != D.S)
	{
		dis[i][D.S] = dis[D.S][i] = getDistance(i , D.S);
		diam = max(diam , dis[i][D.S]);
	}
	int ans = dis[D.F][D.S];
	for(int x = 0 ; x < n ; x++)
	{
		r[x] = (dis[x][D.F] + dis[x][D.S] - dis[D.F][D.S]) / 2;
		R[x] = dis[x][D.S] - r[x];
		L[x] = diam - R[x];
		ans = min(ans , max(L[x] , R[x]));
	}
	ans = -ans;
	set <int> st;
	for(int x = 0 ; x < n ; x++)  if(L[x] == abs(ans) || R[x] == abs(ans))
	{
		st.insert(L[x]);
	}
	if(st.size() == 2)
	{
		int lef = 0 , rig = 0;
		for(int i = 0 ; i < n ; i++)
		{
			if(L[i] <= *st.begin())
				lef++;
			else
				rig++;
		}
		if(lef > n / 2)
		{
			auto it = st.end();  it--;
			auto now = *it;
			st.erase(it);
		}
		else if(rig > n / 2)
		{
			auto now = *st.begin();
			st.erase(now);
		}
		else
		{
			return abs(ans);
		}
	}
	for(auto ch : st) if(Solve(ch))
		ans = abs(ans);
	return ans;
}

Compilation message (stderr)

towns.cpp: In function 'int hubDistance(int, int)':
towns.cpp:108:9: warning: unused variable 'now' [-Wunused-variable]
  108 |    auto now = *it;
      |         ^~~
towns.cpp:66:30: warning: unused parameter 'sub' [-Wunused-parameter]
   66 | int hubDistance(int nn , int sub) {
      |                          ~~~~^~~

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