#1151728 (C++23) No.3469 ジャッジ結果の逆転数

• 問題: No.3469 ジャッジ結果の逆転数
• ユーザー: zawakasu
• 提出日時: 2026-03-06 22:51:27
• 言語: C++23 (gcc 15.2.0 + boost 1.89.0)
• 結果: AC
• 実行時間: 53 ms / 2,000 ms
• コード長: 4,461 bytes
• コンパイル時間: 2,036 ms
• コンパイル使用メモリ: 213,756 KB
• 実行使用メモリ: 7,848 KB
• 最終ジャッジ日時: 2026-03-06 22:51:51
• 合計ジャッジ時間: 3,223 ms
• ジャッジサーバーID （参考情報）: judge2 / judge3

ファイルパターン	結果
sample	AC * 3
other	AC * 17

ソースコード

#include <iostream>
#include <iomanip>
#include <cassert>
#include <vector>
#include <algorithm>
#include <utility>
#include <numeric>
#include <tuple>
#include <ranges>
#include <random>
// #include "Src/Number/IntegerDivision.hpp"
// #include "Src/Utility/BinarySearch.hpp"
// #include "Src/Sequence/CompressedSequence.hpp"
// #include "Src/Sequence/RunLengthEncoding.hpp"
// #include "Src/Algebra/Group/AdditiveGroup.hpp"
// #include "Src/DataStructure/FenwickTree/FenwickTree.hpp"
// #include "Src/DataStructure/SegmentTree/SegmentTree.hpp"
// #include "Src/DataStructure/DisjointSetUnion/DisjointSetUnion.hpp"
// #include "Src/DataStructure/Heap/BinaryHeap.hpp"


#include <cstdint>
#include <cstddef>

namespace zawa {

using i16 = std::int16_t;
using i32 = std::int32_t;
using i64 = std::int64_t;
using i128 = __int128_t;

using u8 = std::uint8_t;
using u16 = std::uint16_t;
using u32 = std::uint32_t;
using u64 = std::uint64_t;

using usize = std::size_t;

} // namespace zawa

#include <iterator>
#include <type_traits>

namespace zawa {

template <class InputIterator>
u64 InversionNumber(InputIterator first, InputIterator last) {
    assert((usize)std::distance(first, last) >= usize{0});
    std::vector<std::remove_reference_t<decltype(*first)>> A(first, last);
    auto rec{[&](auto rec, usize L, usize R) -> u64 {
        if (R - L <= usize{1}) return 0; 
        usize M{(L + R) >> 1};
        u64 res{rec(rec, L, M) + rec(rec, M, R)};
        std::vector<u64> tmp(R - L);
        usize i{L}, j{M}, k{};
        while (i < M and j < R) {
            if (A[i] <= A[j]) {
                tmp[k++] = A[i++];
            }
            else {
                res += M - i;
                tmp[k++] = A[j++];
            }
        }
        while (i < M) tmp[k++] = A[i++];
        while (j < R) tmp[k++] = A[j++];
        for (usize l{L} ; l < R ; l++) {
            A[l] = tmp[l - L];
        }
        return res;
    }};
    return rec(rec, usize{0}, usize{A.size()});
}

template <class InputIterator>
bool InversionParity(InputIterator first, InputIterator last) {
    assert((usize)std::distance(first, last) >= usize{0});
    std::vector<std::remove_reference_t<decltype(*first)>> A(first, last);
    auto rec{[&](auto rec, usize L, usize R) -> bool {
        if (R - L <= usize{1}) return 0; 
        usize M{(L + R) >> 1};
        bool res{rec(rec, L, M) != rec(rec, M, R)};
        std::vector<u64> tmp(R - L);
        usize i{L}, j{M}, k{};
        while (i < M and j < R) {
            if (A[i] <= A[j]) {
                tmp[k++] = A[i++];
            }
            else {
                res ^= (M - i) & 1;
                tmp[k++] = A[j++];
            }
        }
        while (i < M) tmp[k++] = A[i++];
        while (j < R) tmp[k++] = A[j++];
        for (usize l{L} ; l < R ; l++) {
            A[l] = tmp[l - L];
        }
        return res;
    }};
    return rec(rec, usize{0}, usize{A.size()});
}

} // namespace zawa
namespace zawa {}
using namespace zawa;
// #include "atcoder/modint"
// using mint = atcoder::modint998244353;
// #include <array>
// #include <bit>
// #include <bitset>
// #include <climits>
// #include <cmath>
// #include <set>
// #include <unordered_set>
// #include <map>
// #include <unordered_map>
// #include <optional>
// #include <queue>
// #include <stack>
// #include <deque>
// #pragma GCC target("avx2")
// #pragma GCC optimize("O3")
// #pragma GCC optimize("unroll-loops")
using namespace std;
template <class T, class U>
ostream& operator<<(ostream& os, const pair<T, U>& p) {
    os << '(' << p.first << ',' << p.second << ')';
    return os;
}
template <class T>
ostream& operator<<(ostream& os, const vector<T>& v) {
    for (int i = 0 ; i < ssize(v) ; i++)
        os << v[i] << (i + 1 == ssize(v) ? "" : " ");
    return os;
}
int main() {
    cin.tie(0);
    cout.tie(0);
    ios::sync_with_stdio(0);
    cout << fixed << setprecision(20);
#if !defined DEBUG
    int N;
    cin >> N;
    vector<int> A(N);
    for (auto& x : A)
        cin >> x;
    cout << InversionNumber(A.begin(),A.end()) << '\n'; 
#else
    mt19937_64 mt{random_device{}()};
    for (int testcase = 0 ; ; ) {
        cerr << "----------" << ++testcase << "----------" << endl;
        
        auto a = solve(), b = naive();
        if (a != b) {
            // print testcase

            cerr << "you: " << a << endl;
            cout << "correct: " << b << endl;
            exit(0);
        }
    }
#endif
}