Submission #536513

#	Time	Username	Problem	Language	Result	Execution time	Memory
536513		fcw	Hacker (BOI15_hac)	C++17	100 / 100	76 ms	27708 KiB

hac

#include <bits/stdc++.h>
#define st first
#define nd second
using lint = int64_t;
constexpr int mod = int(1e9) + 7;
constexpr int inf = 0x3f3f3f3f;
constexpr int ninf = 0xcfcfcfcf;
constexpr lint linf = 0x3f3f3f3f3f3f3f3f;
const long double pi = acosl(-1.0);
// Returns -1 if a < b, 0 if a = b and 1 if a > b.
int cmp_double(double a, double b = 0, double eps = 1e-9) {
	return a + eps > b ? b + eps > a ? 0 : 1 : -1;
}
using namespace std;

template<typename T, T (*op)(const T&, const T&)> struct monotonic_queue {
    vector<T> as, aas;
    vector<T> bs, bbs;
    void reserve(int N) {
        as.reserve(N); aas.reserve(N);
        bs.reserve(N); bbs.reserve(N);
    }
    void reduce() {
        while (!bs.empty()) {
            as.push_back(bs.back());
            aas.push_back(aas.empty() ? bs.back() : op(bs.back(), aas.back()));
            bs.pop_back(); bbs.pop_back();
        }
    }
    T get() {
        if (as.empty()) reduce();
        return (bbs.empty() ? aas.back() : op(aas.back(), bbs.back()));
    }
    bool empty() const { return (as.empty() && bs.empty()); }
    int size() const { return int(as.size()) + int(bs.size()); }
    T front() {
        if (as.empty()) reduce();
        return as.back();
    }
    void push(const T& val) {
        bs.push_back(val);
        bbs.push_back(bbs.empty() ? val : op(bbs.back(), val));
    }
    void pop() {
        if (as.empty()) reduce();
        as.pop_back();
        aas.pop_back();
    }
};

// min/max
template<typename T> T mapping_max(const T& a, const T& b) {
	return max(a, b);
}
template<typename T> using max_monotonic_queue = monotonic_queue<T, mapping_max>;

int main() {
	cin.tie(nullptr)->sync_with_stdio(false);
	int n;
	cin>>n;
	vector<lint>v(n+n), pref(n+n+1);
	for(int i=0;i<n;i++) cin>>v[i], v[i+n] = v[i];
	for(int i=1;i<=n+n;i++){
		pref[i] = pref[i-1] + v[i-1];
	}
	max_monotonic_queue<lint>q;
	for(int i=1;i+n/2<=n;i++){
		q.push(pref[i+n/2-1] - pref[i-1]);
	}
	lint ans = linf;
	for(int i=0;i<n;i++){
		ans = min(ans, q.get());
		q.pop();
		q.push(pref[n+i] - pref[n+i-n/2]);
	}
	cout<<pref[n] - ans<<"\n";




	return 0;
}
/*
[  ]Leu o problema certo???
[  ]Ver se precisa de long long
[  ]Viu o limite dos fors (é n? é m?)
[  ]Tamanho do vetor, será que é 2e5 em vez de 1e5??
[  ]Testar sample
[  ]Testar casos de  borda
[  ]1LL no 1LL << i
[  ]Testar mod (é 1e9+7, mesmo?, será que o mod não ficou negativo?)
*/

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