結果

問題 No.2327 Inversion Sum
ユーザー phocom
提出日時 2023-05-12 08:53:54
言語 C++17
(gcc 13.3.0 + boost 1.87.0)
結果
AC  
実行時間 40 ms / 2,000 ms
コード長 3,171 bytes
コンパイル時間 988 ms
コンパイル使用メモリ 120,616 KB
最終ジャッジ日時 2025-02-12 21:36:33
ジャッジサーバーID
(参考情報)
judge5 / judge4
このコードへのチャレンジ
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ファイルパターン 結果
sample AC * 3
other AC * 30
権限があれば一括ダウンロードができます

ソースコード

diff #
プレゼンテーションモードにする

#include <iostream>
#include <vector>
#include <set>
#include <unordered_set>
#include <map>
#include <unordered_map>
#include <cstdio>
#include <bitset>
#include <queue>
#include <deque>
#include <algorithm>
#include <numeric>
#include <cassert>
#include <functional>
#include <stack>
#include <cmath>
#include <string>
#include <complex>
#include <cassert>
#define REP(i, N) for (int i = 0; i < (int)N; i++)
#define FOR(i, a, b) for (int i = a; i < (int)b; i++)
#define ALL(x) (x).begin(), (x).end()
using namespace std;
constexpr int mod = 998244353;
template <int mod>
struct ModInt {
int x;
ModInt() : x(0) {}
ModInt(int64_t y) : x(y >= 0 ? y % mod : (mod - (-y) % mod) % mod) {}
ModInt& operator+=(const ModInt& p) {
if ((x += p.x) >= mod) x -= mod;
return *this;
}
ModInt& operator-=(const ModInt& p) {
if ((x += mod - p.x) >= mod) x -= mod;
return *this;
}
ModInt& operator*=(const ModInt& p) {
x = (int)(1LL * x * p.x % mod);
return *this;
}
ModInt& operator/=(const ModInt& p) {
*this *= p.inverse();
return *this;
}
ModInt operator-() const { return ModInt(-x); }
ModInt operator+(const ModInt& p) const { return ModInt(*this) += p; }
ModInt operator-(const ModInt& p) const { return ModInt(*this) -= p; }
ModInt operator*(const ModInt& p) const { return ModInt(*this) *= p; }
ModInt operator/(const ModInt& p) const { return ModInt(*this) /= p; }
ModInt inverse() const {
int a = x, b = mod, u = 1, v = 0, t;
while (b > 0) {
t = a / b;
swap(a -= t * b, b);
swap(u -= t * v, v);
}
return ModInt(u);
}
ModInt pow(int64_t n) const {
ModInt ret(1), mul(x);
while (n > 0) {
if (n & 1) ret *= mul;
mul *= mul;
n >>= 1;
}
return ret;
}
friend ostream& operator<<(ostream& os, const ModInt& p) { return os << p.x; }
friend istream& operator>>(istream& is, ModInt& a) {
int64_t t;
is >> t;
a = ModInt<mod>(t);
return (is);
}
static int get_mod() { return mod; }
};
using modint = ModInt<mod>;
template <typename T>
struct BinaryIndexedTree {
vector<T> data;
BinaryIndexedTree(int sz) { data.assign(++sz, 0); }
T sum(int k) {
T ret = 0;
for (++k; k > 0; k -= k & -k) ret += data[k];
return (ret);
}
void add(int k, T x) {
for (++k; k < data.size(); k += k & -k) data[k] += x;
}
};
int main() {
int N, M;
cin >> N >> M;
int R = N - M;
vector<int> A(N, -1), used(N), cum(N + 1);
REP(i, M) {
int P, K;
cin >> P >> K;
A[K - 1] = P - 1;
used[P - 1] = 1;
}
vector<int> rest;
REP(i, N) {
if (!used[i]) rest.push_back(i);
cum[i + 1] = cum[i] + (A[i] == -1);
}
vector<modint> facts(N + 1, 1);
FOR(i, 2, N + 1) facts[i] = facts[i - 1] * i;
BinaryIndexedTree<int> bit(N + 1);
modint ans = facts[R] * R * (R - 1) / 4;
int B = 0;
REP(i, N) {
if (A[i] != -1) {
long long C = rest.end() - lower_bound(ALL(rest), A[i]);
ans += facts[R - 1] * (C * cum[i] + (R - C) * (cum[N] - cum[i + 1]));
ans += facts[R] * (i - cum[i] - bit.sum(A[i]));
bit.add(A[i], 1);
}
}
cout << ans << endl;
return 0;
}
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