結果

問題 No.2616 中央番目の中央値
ユーザー 👑 binap
提出日時 2024-01-26 21:58:10
言語 C++17
(gcc 13.3.0 + boost 1.87.0)
結果
AC  
実行時間 293 ms / 2,000 ms
コード長 2,975 bytes
コンパイル時間 4,311 ms
コンパイル使用メモリ 258,376 KB
最終ジャッジ日時 2025-02-18 23:13:36
ジャッジサーバーID
(参考情報)
judge1 / judge4
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ファイルパターン 結果
other AC * 37
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ソースコード

diff #
プレゼンテーションモードにする

#include<bits/stdc++.h>
#include<atcoder/all>
#define rep(i,n) for(int i=0;i<n;i++)
using namespace std;
using namespace atcoder;
typedef long long ll;
typedef vector<int> vi;
typedef vector<long long> vl;
typedef vector<vector<int>> vvi;
typedef vector<vector<long long>> vvl;
typedef long double ld;
typedef pair<int, int> P;
ostream& operator<<(ostream& os, const modint& a) {os << a.val(); return os;}
template <int m> ostream& operator<<(ostream& os, const static_modint<m>& a) {os << a.val(); return os;}
template<typename T> istream& operator>>(istream& is, vector<T>& v){int n = v.size(); assert(n > 0); rep(i, n) is >> v[i]; return is;}
template<typename U, typename T> ostream& operator<<(ostream& os, const pair<U, T>& p){os << p.first << ' ' << p.second; return os;}
template<typename T> ostream& operator<<(ostream& os, const vector<T>& v){int n = v.size(); rep(i, n) os << v[i] << (i == n - 1 ? "\n" : " "); return
    os;}
template<typename T> ostream& operator<<(ostream& os, const vector<vector<T>>& v){int n = v.size(); rep(i, n) os << v[i] << (i == n - 1 ? "\n" : "");
    return os;}
template<typename T> void chmin(T& a, T b){a = min(a, b);}
template<typename T> void chmax(T& a, T b){a = max(a, b);}
using mint = modint998244353;
// combination mod prime
// https://youtu.be/8uowVvQ_-Mo?t=6002
// https://youtu.be/Tgd_zLfRZOQ?t=9928
struct modinv {
int n; vector<mint> d;
modinv(): n(2), d({0,1}) {}
mint operator()(int i) {
while (n <= i) d.push_back(-d[mint::mod()%n]*(mint::mod()/n)), ++n;
return d[i];
}
mint operator[](int i) const { return d[i];}
} invs;
struct modfact {
int n; vector<mint> d;
modfact(): n(2), d({1,1}) {}
mint operator()(int i) {
while (n <= i) d.push_back(d.back()*n), ++n;
return d[i];
}
mint operator[](int i) const { return d[i];}
} facts;
struct modfactinv {
int n; vector<mint> d;
modfactinv(): n(2), d({1,1}) {}
mint operator()(int i) {
while (n <= i) d.push_back(d.back()*invs(n)), ++n;
return d[i];
}
mint operator[](int i) const { return d[i];}
} ifacts;
mint comb(int n, int k) {
if (n < k || k < 0) return 0;
return facts(n)*ifacts(k)*ifacts(n-k);
}
using S = int;
S op(S a, S b){
return a + b;
}
S e(){
return 0;
}
int main(){
int n;
cin >> n;
vector<int> p(n);
cin >> p;
rep(i, n) p[i]--;
vector<int> s1(n), s2(n), l1(n), l2(n);
{
segtree<S, op, e> seg(n);
rep(i, n){
s1[i] = seg.prod(p[i], n);
l1[i] = seg.prod(0, p[i]);
seg.set(p[i], 1);
}
}
{
reverse(p.begin(), p.end());
segtree<S, op, e> seg(n);
rep(i, n){
s2[i] = seg.prod(p[i], n);
l2[i] = seg.prod(0, p[i]);
seg.set(p[i], 1);
}
reverse(s2.begin(), s2.end());
reverse(l2.begin(), l2.end());
reverse(p.begin(), p.end());
}
mint ans = 0;
rep(i, n){
// cout << s1[i] << ' ' << l1[i] << ' ' << s2[i] << ' ' << l2[i] << "\n";
ans += comb(s1[i] + l2[i], min(s1[i], l2[i])) * comb(s2[i] + l1[i], min(s2[i], l1[i]));
}
cout << ans << "\n";
return 0;
}
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