#1179033 (C++23) No.3646 Decrement.

• 問題: No.3646 Decrement.
• ユーザー: Forested
• 提出日時: 2026-08-25 15:14:50
• 言語: C++23 (gcc 15.2.0 + boost 1.90.0)
• 結果: AC
• 実行時間: 41 ms / 2,000 ms
• コード長: 5,469 bytes
• コンパイル時間: 2,336 ms
• コンパイル使用メモリ: 347,108 KB
• 実行使用メモリ: 11,552 KB
• 最終ジャッジ日時: 2026-08-25 15:14:56
• 合計ジャッジ時間: 5,229 ms
• ジャッジサーバーID （参考情報）: judge2_0 / judge1_0

サブタスク	配点	結果
サンプル	0 %	AC * 1
小課題1	5 %	AC * 5
小課題2	5 %	AC * 3
小課題3	20 %	AC * 10
小課題4	30 %	AC * 19
小課題5	10 %	AC * 34
小課題6	30 %	AC * 45
合計	100 点

ソースコード

#ifndef LOCAL
#define FAST_IO
#endif

// ============
#include <bits/stdc++.h>
#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 PER2(i, n) for (i32 i = (i32)(n)-1; i >= 0; --i)
#define PER3(i, m, n) for (i32 i = (i32)(n)-1; i >= (i32)(m); --i)
#define PER(...) OVERRIDE(__VA_ARGS__, PER3, PER2)(__VA_ARGS__)
#define ALL(x) begin(x), end(x)
#define LEN(x) (i32)(x.size())
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;
using pi = pair<i32, i32>;
using pl = pair<i64, i64>;
template <typename T>
using V = vector<T>;
template <typename T>
using VV = V<V<T>>;
template <typename T>
using VVV = V<V<V<T>>>;
template <typename T>
using VVVV = V<V<V<V<T>>>>;
template <typename T>
using PQR = priority_queue<T, V<T>, greater<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;
}
template <typename T>
i32 lob(const V<T> &arr, const T &v) {
    return (i32)(lower_bound(ALL(arr), v) - arr.begin());
}
template <typename T>
i32 upb(const V<T> &arr, const T &v) {
    return (i32)(upper_bound(ALL(arr), v) - arr.begin());
}
template <typename T>
V<i32> argsort(const V<T> &arr) {
    V<i32> ret(arr.size());
    iota(ALL(ret), 0);
    sort(ALL(ret), [&](i32 i, i32 j) -> bool {
        if (arr[i] == arr[j]) {
            return i < j;
        } else {
            return arr[i] < arr[j];
        }
    });
    return ret;
}
#ifdef INT128
using u128 = __uint128_t;
using i128 = __int128_t;
#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;
void scan(char &x) { cin >> x; }
void scan(u32 &x) { cin >> x; }
void scan(u64 &x) { cin >> x; }
void scan(i32 &x) { cin >> x; }
void scan(i64 &x) { cin >> x; }
void scan(f64 &x) { cin >> x; }
void scan(string &x) { cin >> x; }
template <typename T>
void scan(V<T> &x) {
    for (T &ele : x) {
        scan(ele);
    }
}
void read() {}
template <typename Head, typename... Tail>
void read(Head &head, Tail &...tail) {
    scan(head);
    read(tail...);
}
#define CHAR(...)     \
    char __VA_ARGS__; \
    read(__VA_ARGS__);
#define U32(...)     \
    u32 __VA_ARGS__; \
    read(__VA_ARGS__);
#define U64(...)     \
    u64 __VA_ARGS__; \
    read(__VA_ARGS__);
#define I32(...)     \
    i32 __VA_ARGS__; \
    read(__VA_ARGS__);
#define I64(...)     \
    i64 __VA_ARGS__; \
    read(__VA_ARGS__);
#define F64(...)     \
    f64 __VA_ARGS__; \
    read(__VA_ARGS__);
#define STR(...)        \
    string __VA_ARGS__; \
    read(__VA_ARGS__);
#define VEC(type, name, size) \
    V<type> name(size);       \
    read(name);
#define VVEC(type, name, size1, size2)    \
    VV<type> name(size1, V<type>(size2)); \
    read(name);
// ============

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

// ============

#include <vector>

template <typename T, typename Compare = std::less<T>>
std::vector<int> cartesian_tree(const std::vector<T> &a, Compare comp = Compare()) {
    std::vector<int> stc;
    std::vector<int> par(a.size(), -1);
    for (int i = 0; i < a.size(); ++i) {
        while (stc.size() >= 2 && comp(a[i], a[stc.back()])) {
            if (comp(a[i], a[stc[stc.size() - 2]])) {
                par[stc.back()] = stc[stc.size() - 2];
            } else {
                par[stc.back()] = i;
            }
            stc.pop_back();
        }
        if (stc.size() == 1 && comp(a[i], a[stc.back()])) {
            par[stc.back()] = i;
            stc.pop_back();
        }
        stc.push_back(i);
    }
    while (stc.size() >= 2) {
        par[stc.back()] = stc[stc.size() - 2];
        stc.pop_back();
    }
    return par;
}
// ============

void solve() {
    I32(n);
    I64(k);
    VEC(i64, a, n);
    V<i32> par = cartesian_tree(a);
    DBG(par);
    V<i32> lch(n, -1), rch(n, -1);
    i32 root = -1;
    REP(i, n) {
        if (par[i] == -1) {
            root = i;
        } else if (par[i] < i) {
            rch[par[i]] = i;
        } else {
            lch[par[i]] = i;
        }
    }
    V<pair<i32, i64>> rngs;
    {
        auto rec = [&](auto rec, i32 rt, i32 l, i32 r, i64 p) -> void {
            rngs.emplace_back(r - l, a[rt] - p);
            if (lch[rt] != -1) {
                rec(rec, lch[rt], l, rt, a[rt]);
            }
            if (rch[rt] != -1) {
                rec(rec, rch[rt], rt + 1, r, a[rt]);
            }
        };
        rec(rec, root, 0, n, 0);
    }
    i64 ans = a[0] + a[n - 1];
    REP(i, n - 1) {
        ans += abs(a[i] - a[i + 1]);
    }
    sort(ALL(rngs));
    DBG(rngs);
    for (auto [pct, pro] : rngs) {
        i64 can = k / pct;
        if (can <= pro) {
            ans -= 2 * can;
            break;
        }
        k -= pro * pct;
        ans -= 2 * pro;
    }
    cout << ans << '\n';
}

int main() {
    i32 t = 1;
    // cin >> t;
    while (t--) {
        solve();
    }
}