Submission #1036656

#	Time	Username	Problem	Language	Result	Execution time	Memory
1036656		Nonoze	Hacker (BOI15_hac)	C++17	100 / 100	23 ms	5720 KiB

hac

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

namespace std {

// https://judge.yosupo.jp/submission/193613
struct IOPre {
    static constexpr int TEN = 10, SZ = TEN * TEN * TEN * TEN;
    std::array<char, 4 * SZ> num;
    constexpr IOPre() : num{} {
        for (int i = 0; i < SZ; i++) for (int n = i, j = 3; j >= 0; j--) num[i * 4 + j] = n % TEN + '0', n /= TEN;
    }
};

struct IO {
#if !HAVE_DECL_FREAD_UNLOCKED
    #define fread_unlocked fread
#endif
#if !HAVE_DECL_FWRITE_UNLOCKED
    #define fwrite_unlocked fwrite
#endif
    static constexpr int SZ = 1 << 17, LEN = 32, TEN = 10, HUNDRED = TEN * TEN,
                         THOUSAND = HUNDRED * TEN, TENTHOUSAND = THOUSAND * TEN,
                         MAGIC_MULTIPLY = 205, MAGIC_SHIFT = 11, MASK = 15,
                         TWELVE = 12, SIXTEEN = 16;
    static constexpr IOPre io_pre = {};
    std::array<char, SZ> input_buffer, output_buffer;
    int input_ptr_left, input_ptr_right, output_ptr_right;

    IO() : input_buffer{}, output_buffer{}, input_ptr_left{}, input_ptr_right{}, output_ptr_right{} {}
    IO(const IO&) = delete;
    IO(IO&&) = delete;
    IO& operator=(const IO&) = delete;
    IO& operator=(IO&&) = delete;
    ~IO() { flush(); }

    template<typename T> static constexpr bool is_char_v    = std::is_same_v<T, char>;
    template<typename T> static constexpr bool is_bool_v    = std::is_same_v<T, bool>;
    template<typename T> static constexpr bool is_string_v  =
            std::is_same_v<T, std::string> || std::is_same_v<T, const char*> ||
            std::is_same_v<T, char*> || std::is_same_v< std::decay_t<T>, char*>;
    template<typename T> static constexpr bool is_default_v =
            is_char_v<T> || is_bool_v<T> || is_string_v<T> || std::is_integral_v<T>;

    inline void load() {
        memmove(std::begin(input_buffer),
                std::begin(input_buffer) + input_ptr_left,
                input_ptr_right - input_ptr_left);
        input_ptr_right =
            input_ptr_right - input_ptr_left +
            fread_unlocked(
                std::begin(input_buffer) + input_ptr_right - input_ptr_left, 1,
                SZ - input_ptr_right + input_ptr_left, stdin);
        input_ptr_left = 0;
    }

    inline void read_char(char& c) {
        if (input_ptr_left + LEN > input_ptr_right) load();
        c = input_buffer[input_ptr_left++];
    }
    inline void read_string(std::string& x) {
        char c;
        while (read_char(c), c < '!') continue;
        x = c;
        while (read_char(c), c >= '!') x += c;
    }
    template<typename T>
    inline std::enable_if_t<std::is_integral_v<T>, void> read_int(T& x) {
        if (input_ptr_left + LEN > input_ptr_right) load();
        char c = 0;
        do c = input_buffer[input_ptr_left++];
        while (c < '-');
        [[maybe_unused]] bool minus = false;
        if constexpr (std::is_signed<T>::value == true)
            if (c == '-') minus = true, c = input_buffer[input_ptr_left++];
        x = 0;
        while (c >= '0')
            x = x * TEN + (c & MASK), c = input_buffer[input_ptr_left++];
        if constexpr (std::is_signed<T>::value == true)
            if (minus) x = -x;
    }

    inline void skip_space() {
        if (input_ptr_left + LEN > input_ptr_right) load();
        while (input_buffer[input_ptr_left] <= ' ') input_ptr_left++;
    }

    inline void flush() {
        fwrite_unlocked(std::begin(output_buffer), 1, output_ptr_right, stdout);
        output_ptr_right = 0;
    }

    inline void write_char(char c) {
        if (output_ptr_right > SZ - LEN) flush();
        output_buffer[output_ptr_right++] = c;
    }

    inline void write_bool(bool b) {
        if (output_ptr_right > SZ - LEN) flush();
        output_buffer[output_ptr_right++] = b ? '1' : '0';
    }

    inline void write_string(const std::string& s) {
        for (auto x : s) write_char(x);
    }

    inline void write_string(const char* s) {
        while (*s) write_char(*s++);
    }

    inline void write_string(char* s) {
        while (*s) write_char(*s++);
    }

    template <typename T>
    inline std::enable_if_t< std::is_integral_v<T>, void> write_int(T x) {
        if (output_ptr_right > SZ - LEN) flush();
        if (!x) {
            output_buffer[output_ptr_right++] = '0';
            return;
        }
        if constexpr (std::is_signed_v<T>) if (x < 0) output_buffer[output_ptr_right++] = '-', x = -x;
        int i = TWELVE;
        std::array<char, SIXTEEN> buf{};
        for (; x >= TENTHOUSAND; x /= TENTHOUSAND, i -= 4)
            memcpy(std::begin(buf) + i, std::begin(io_pre.num) + (x % TENTHOUSAND) * 4, 4);
        if (x < HUNDRED) {
            if (x < TEN) output_buffer[output_ptr_right++] = '0' + x;
            else {
                uint32_t q = (uint32_t(x) * MAGIC_MULTIPLY) >> MAGIC_SHIFT;
                uint32_t r = uint32_t(x) - q * TEN;
                output_buffer[output_ptr_right++] = '0' + q;
                output_buffer[output_ptr_right++] = '0' + r;
            }
        } else {
            if (x < THOUSAND) 
                memcpy(std::begin(output_buffer) + output_ptr_right, std::begin(io_pre.num) + (x << 2) + 1, 3),
                output_ptr_right += 3;
            else
                memcpy(std::begin(output_buffer) + output_ptr_right, std::begin(io_pre.num) + (x << 2), 4),
                output_ptr_right += 4;
        }
        memcpy(std::begin(output_buffer) + output_ptr_right, std::begin(buf) + i + 4, TWELVE - i);
        output_ptr_right += TWELVE - i;
    }

    template <typename T_>
    std::enable_if_t<(is_default_v< std::remove_cv_t< std::remove_reference_t<T_> > >), IO&> operator<<(T_&& x) {
        using T = std::remove_cv_t< std::remove_reference_t<T_> >;
        if constexpr (is_bool_v<T>) write_bool(x);
        else if constexpr (is_string_v<T>) write_string(x);
        else if constexpr (is_char_v<T>) write_char(x);
        else if constexpr (std::is_integral_v<T>) write_int(x);
        return *this;
    }

    template<typename T>
    std::enable_if_t<(is_default_v<T> && !is_bool_v<T>), IO&> operator>>(T& x) {
        if constexpr (is_string_v<T>) read_string(x);
        else if constexpr (is_char_v<T>) read_char(x);
        else if constexpr (std::is_integral_v<T>) read_int(x);
        return *this;
    }

    IO* tie(std::nullptr_t) { return this; }
    void sync_with_stdio(bool) {}
} io;

} // namespace std

using std::io;

#define cin io
#define cout io


#define sz(x) (int)(x.size())
#define debug(x) cerr << (#x) << ": " << (x) << endl
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
int n, k, m;
vector<int> a;

void solve() {
	cin >> n;
	a.clear(), a.resize(n);
	for (auto &u: a) cin >> u;
	vector<int> sum(n, 0);
	int mid=n/2+n%2;
	for (int i=0; i<mid; i++) sum[0]+=a[i];
	for (int i=1; i<n; i++) {
		sum[i]=sum[i-1]+a[(i+mid-1)%n]-a[i-1];
	}
	deque<int> curr;
	for (int i=0; i<mid; i++) {
		while (!curr.empty() && sum[curr.front()]>=sum[i]) curr.pop_front();
		curr.push_front(i);
	}
	int ans=0;
	for (int i=mid; i<n+mid; i++) {
		ans=max(ans, sum[curr.back()]);
		while (!curr.empty() && sum[curr.front()]>=sum[i%n]) curr.pop_front();
		if (!curr.empty() && curr.back()==i-mid) curr.pop_back();
		curr.push_front(i%n);
	}
	cout << ans;
	return;
}

signed main() {
	ios::sync_with_stdio(0);
	cin.tie(0);
	int tt=1;// cin >> tt;
	while(tt--) solve();
	return 0;
}

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