Submission #854911

#	Time	Username	Problem	Language	Result	Execution time	Memory
854911		Forested	Discharging (NOI20_discharging)	C++17	100 / 100	94 ms	25696 KiB

Discharging

#ifndef LOCAL
#define FAST_IO
#endif

// ============
#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <charconv>
#include <cmath>
#include <cstring>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

#define OVERRIDE(a, b, c, d, ...) d
#define REP2(i, n) for (i32 i = 0; i < (i32)(n); ++i)
#define REP3(i, m, n) for (i32 i = (i32)(m); i < (i32)(n); ++i)
#define REP(...) OVERRIDE(__VA_ARGS__, REP3, REP2)(__VA_ARGS__)
#define PER(i, n) for (i32 i = (i32)(n) - 1; i >= 0; --i)
#define ALL(x) begin(x), end(x)

using namespace std;

using u32 = unsigned int;
using u64 = unsigned long long;
using i32 = signed int;
using i64 = signed long long;
using f64 = double;
using f80 = long double;

template <typename T>
using Vec = vector<T>;

template <typename T>
bool chmin(T &x, const T &y) {
    if (x > y) {
        x = y;
        return true;
    }
    return false;
}
template <typename T>
bool chmax(T &x, const T &y) {
    if (x < y) {
        x = y;
        return true;
    }
    return false;
}

#ifdef INT128

using u128 = __uint128_t;
using i128 = __int128_t;

istream &operator>>(istream &is, i128 &x) {
    i64 v;
    is >> v;
    x = v;
    return is;
}
ostream &operator<<(ostream &os, i128 x) {
    os << (i64)x;
    return os;
}
istream &operator>>(istream &is, u128 &x) {
    u64 v;
    is >> v;
    x = v;
    return is;
}
ostream &operator<<(ostream &os, u128 x) {
    os << (u64)x;
    return os;
}

#endif

[[maybe_unused]] constexpr i32 INF = 1000000100;
[[maybe_unused]] constexpr i64 INF64 = 3000000000000000100;
struct SetUpIO {
    SetUpIO() {
#ifdef FAST_IO
        ios::sync_with_stdio(false);
        cin.tie(nullptr);
#endif
        cout << fixed << setprecision(15);
    }
} set_up_io;
// ============

#ifdef DEBUGF
#else
#define DBG(x) (void)0
#endif

class CHT {
    struct Line {
        i64 a, b;
        i64 operator()(i64 x) const {
            return a * x + b;
        }
    };
    static i64 inter(Line l0, Line l1) {
        assert(l0.a > l1.a);
        i64 ret = (l1.b - l0.b) / (l0.a - l1.a);
        /*if (l1.b - l0.b < 0 && (l1.b - l0.b) % (l0.a - l1.a) != 0) {
            ret -= 1;
        }*/
        return ret;
    }
    deque<Line> lines;
public:
    CHT() : lines() {}
    void add(i64 a, i64 b) {
        if (!lines.empty() && lines.back().a == a) {
            if (lines.back().b > b) {
                lines.pop_back();
            } else {
                return;
            }
        }
        if (!lines.empty()) {
            assert(lines.back().a > a);
        }
        Line line{a, b};
        while (lines.size() >= 2 && inter(lines[lines.size() - 2], lines.back()) >= inter(lines.back(), line)) {
            lines.pop_back();
        }
        lines.push_back(line);
    }
    i64 get(i64 x) {
        assert(!lines.empty());
        while (lines.size() >= 2 && lines[0](x) > lines[1](x)) {
            lines.pop_front();
        }
        return lines.front()(x);
    }
};

int main() {
    i32 n;
    cin >> n;
    Vec<i64> t(n);
    REP(i, n) {
        cin >> t[i];
    }
    REP(i, n - 1) {
        chmax(t[i + 1], t[i]);
    }
    reverse(ALL(t));
    Vec<i64> dp(n + 1, 0);
    CHT cht;
    REP(i, n) {
        cht.add(t[i], dp[i]);
        dp[i + 1] = cht.get(i + 1);
    }
    cout << dp[n] << '\n';
}

• Subtask 1: 9 / 9
• Subtask 2: 13 / 13
• Subtask 3: 25 / 25
• Subtask 4: 11 / 11
• Subtask 5: 14 / 14
• Subtask 6: 28 / 28