Submission #1056617

#	Time	Username	Problem	Language	Result	Execution time	Memory
1056617		parsadox2	Radio Towers (IOI22_towers)	C++17	58 / 100	4019 ms	17616 KiB

towers

#include <bits/stdc++.h>
#include "towers.h"
 
using namespace std;
 
const int N = 1e5 + 10 , inf = 1e9 , Lg = 17;
 
int n , a[N] , rmxq[N][Lg] , rmnq[N][Lg] , lg2[N] , nexL[N] , nexR[N];
int b[N] , psum[N];
vector <int> all;
 
int mn_pos(int aa , int bb)
{
	if(a[aa] < a[bb])
		return aa;
	return bb;
}
 
int mx_pos(int aa , int bb)
{
	if(a[aa] > a[bb])
		return aa;
	return bb;
}
 
int Get_mx(int l , int r)
{
	r++;
	int sz = (r - l);  sz = lg2[sz];
	return mx_pos(rmxq[l][sz] , rmxq[r - (1 << sz)][sz]);
}
 
int Get_mn(int l , int r)
{
	r++;
	int sz = (r - l);  sz = lg2[sz];
	return mn_pos(rmnq[l][sz] , rmnq[r - (1 << sz)][sz]);
}


void Build()
{
	lg2[1] = 0;
	for(int i = 2 ; i < N ; i++)
		lg2[i] = lg2[i / 2] + 1;
	for(int i = 0 ; i < n ; i++)
		rmnq[i][0] = rmxq[i][0] = i;
	for(int j = 1 ; j < Lg ; j++)
	{
		int len = (1 << j);
		for(int i = 0 ; i + len <= n ; i++)
		{
			rmnq[i][j] = mn_pos(rmnq[i][j - 1] , rmnq[i + len / 2][j - 1]);
			rmxq[i][j] = mx_pos(rmxq[i][j - 1] , rmxq[i + len / 2][j - 1]);
		}
	}
	for(int i = 1 ; i + 1 < n ; i++)  if(a[i] > a[i - 1] && a[i] > a[i + 1])
		b[i] = 1;
	for(int i = 1 ; i < n ; i++)
		psum[i] = psum[i - 1] + b[i];
	vector <int> st;
	for(int i = 0 ; i < n ; i++)
	{
		nexL[i] = -1;
		nexR[i] = n;
		while(!st.empty())
		{
			if(a[st.back()] < a[i])
			{
				nexR[st.back()] = i;
				st.pop_back();
			}
			else
			{
				nexL[i] = st.back();
				break;
			}
		}
		st.push_back(i);
	}
	for(int i = 0 ; i < n ; i++)  if(i - nexL[i] > 1 && nexR[i] - i > 1)
	{
		int lc = Get_mn(nexL[i] + 1 , i - 1) , rc = Get_mn(i + 1 , nexR[i] - 1);
		all.push_back(a[i] - max(a[lc] , a[rc]));
	}
	sort(all.begin() , all.end());
}
 
void init(int nn , vector <int> vec)
{
	n = nn;
	for(int i = 0 ; i < n ; i++)
		a[i] = vec[i];
	Build();
}
 
int Solve(int l , int r , int d)
{
	if(l > r)
		return 0;
	int pos_mx = Get_mx(l , r);
	int res = Solve(l , pos_mx - 1 , d) + Solve(pos_mx + 1 , r , d);
	if(pos_mx != l && pos_mx != r)
	{
		int lc = Get_mn(l , pos_mx - 1) , rc = Get_mn(pos_mx + 1 , r);
		if(a[pos_mx] - a[lc] >= d && a[pos_mx] - a[rc] >= d)
			res++;
	}
	return res;
}
 
 
int max_towers(int l , int r , int d)
{
	if(d == 1)
	{
		if(l + 1 >= r)
			return 1;
		return 1 + psum[r - 1] - psum[l];
	}
	if(psum[r - 1] - psum[l] == 0)
		return 1;
	if(psum[r - 1] - psum[l] == 1)
	{
		int id = Get_mx(l , r);
		int lc = Get_mn(l , id - 1) , rc = Get_mn(id + 1 , r);
		if(a[id] - d >= a[lc] && a[id] - d >= a[rc])
			return 2;
		return 1;
	}
	if(l == 0 && r == n - 1)
	{
		int id = lower_bound(all.begin() , all.end() , d) - all.begin();
		return all.size() - id + 1;
	}
	return 1 + Solve(l , r , d);
}

• Subtask 1: 4 / 4
• Subtask 2: 11 / 11
• Subtask 3: 12 / 12
• Subtask 4: 14 / 14
• Subtask 5: 17 / 17
• Subtask 6: 0 / 19
• Subtask 7: 0 / 23