Submission #867780

#	Time	Username	Problem	Language	Result	Execution time	Memory
867780		dio_2	Hacker (BOI15_hac)	C++17	100 / 100	174 ms	65384 KiB

hac

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

const int MAX_N = 12 * 500'000;

int ST[MAX_N];
int N, NN;
	
int get_min(int l, int r){
	l += NN, r += NN;
	int res = int(1e9);
	while(l <= r){
		if(l % 2 == 1) res = min(res, ST[l++]);
		if(r % 2 == 0) res = min(res, ST[r--]);
		l /= 2, r /= 2;
	}
	return res;
}

void SET(int pos, int val){
	pos += NN;
	ST[pos] = val;
	for(pos /= 2;pos >= 1;pos /= 2) ST[pos] = min(ST[2 * pos], ST[2 * pos + 1]);
}

int main(){
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	
	for(int i = 0;i < MAX_N;i++) ST[i] = (int)1e9;
	
	cin >> N;
	
	NN = 3 * N;
	
	vector<int> A(N);
	for(int &x : A) cin >> x; // A[i] <= 2000

	for(int i = 0;i < N;i++) A.push_back(A[i]);
	for(int i = 0;i < N;i++) A.push_back(A[i]);
	
	vector<array<int, 3>> wids;
	auto add = [&](int s, int l, int r)->void{
		wids.push_back({s, l, r});
	};
	
	int K = (N + 1) / 2;
	int sum = 0;
	for(int i = 0;i < K;i++){
		sum += A[N-K+i+1];
	}
	
	add(sum, N-K+1, N);
	
	for(int i = N + 1;i < 3 * N;++i){
		sum += A[i];
		sum -= A[i - K];
		add(sum, i - K + 1, i);
	}
	
	vector<int> in(NN, -1), out(NN, -1);
	vector<int> sums;
	int id = 0;
	for(auto [s, l, r] : wids){
		sums.push_back(s);
		swap(l, r);
		if(in[l] == -1) in[l] = id;
		if(out[r] == -1 && in[r] != -1) out[r] = id;
		++id;
	}
	
	int ans = 0;
	
	for(int i = 0;i < (int)sums.size();i++){
		SET(i, sums[i]);
	}
	
	for(int i = 0;i < NN;i++){
		if(in[i] == -1 || out[i] == -1) continue;
		//~ for(int j = in[i];j <= out[i];j++) res = min(res, sums[j]);
		ans = max(ans, get_min(in[i], out[i]));
	}
	
	cout << ans << '\n';
	
	return 0;
}

• Subtask 1: 20 / 20
• Subtask 2: 20 / 20
• Subtask 3: 20 / 20
• Subtask 4: 40 / 40