結果
問題 | No.271 next_permutation (2) |
ユーザー |
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提出日時 | 2020-11-12 09:23:21 |
言語 | C++14 (gcc 13.3.0 + boost 1.87.0) |
結果 |
AC
|
実行時間 | 21 ms / 2,000 ms |
コード長 | 2,929 bytes |
コンパイル時間 | 1,940 ms |
コンパイル使用メモリ | 174,780 KB |
実行使用メモリ | 7,040 KB |
最終ジャッジ日時 | 2024-07-22 19:04:21 |
合計ジャッジ時間 | 2,228 ms |
ジャッジサーバーID (参考情報) |
judge5 / judge3 |
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ファイルパターン | 結果 |
---|---|
other | AC * 21 |
ソースコード
#include "bits/stdc++.h"using namespace std;typedef long long ll;typedef pair<int, int> pii;typedef pair<ll, ll> pll;const int INF = 1e9;const ll LINF = 1e18;template<class S,class T> ostream& operator << (ostream& out,const pair<S,T>& o){ out << "(" << o.first << "," << o.second << ")"; return out; }template<class T> ostream& operator << (ostream& out,const vector<T> V){ for(int i = 0; i < V.size(); i++){ out << V[i]; if(i!=V.size()-1) out << " ";} return out; }template<class T> ostream& operator << (ostream& out,const vector<vector<T> > Mat){ for(int i = 0; i < Mat.size(); i++) { if(i != 0) out << endl; out<< Mat[i];} return out; }template<class S,class T> ostream& operator << (ostream& out,const map<S,T> mp){ out << "{ "; for(auto it = mp.begin(); it != mp.end(); it++){ out <<it->first << ":" << it->second; if(mp.size()-1 != distance(mp.begin(),it)) out << ", "; } out << " }"; return out; }struct BIT {ll N;vector<ll> bit;BIT(ll N):N(N) {bit.resize(N + 1, 0);}void add(ll x, ll val){while (x <= N) {bit[x] += val;x += x & -x;}}ll sum(ll x){ll ret = 0;while (x) {ret += bit[x];x &= (x - 1);}return (ret);}};const ll MOD = 1e9+7;struct FNS{vector<ll> F;vector<ll> fact;ll Inv[5];FNS(vector<ll> permutation):F(permutation.size()),fact(permutation.size()+5){BIT bit(permutation.size());fact[0] = 1;for(ll i = 1; i < fact.size();i++) fact[i] = i*fact[i-1]%MOD;Inv[0] = 0; Inv[1] = 1;for(int i = 2; i < 5;i++) Inv[i] = Inv[MOD%i] * (MOD - MOD/i) % MOD;for(int i = (int)permutation.size()-1; i >= 0; i--){F[i] = bit.sum(permutation[i]);bit.add(permutation[i],1);}}ll add(ll K){for(ll i = 0; i < F.size();i++){ll T = K+F[F.size()-1-i];F[F.size()-1-i]=T%(i+1); K=T/(i+1);}return K;}ll invsum(){ll ret = 0;ll t1 = 0,t2 = 1;for(ll i = F.size()-1; i >= 0; i--){ll n = F.size()-1-i;(ret+=F[i]*fact[n]%MOD*n%MOD*(n-1+MOD)%MOD*Inv[4]%MOD)%=MOD;(ret+=t2*F[i]%MOD*(F[i]-1+MOD)%MOD*Inv[2]%MOD)%=MOD;(ret+=F[i]*t1%MOD)%=MOD;(t1+=F[i]*t2%MOD)%=MOD;(t2*=(F.size()-i+MOD)%MOD)%=MOD;}return ret;}};ll solve(){ll N,K; cin >> N >> K;vector<ll> p(N);for(auto& in:p) cin >> in;FNS fns(p);ll linv = fns.invsum();ll mul = fns.add(K);ll rinv = fns.invsum();ll res = 0;res = mul*fns.fact[N]%MOD*N%MOD*(N-1+MOD)%MOD*fns.Inv[4]%MOD + (rinv - linv + MOD)%MOD;res %= MOD;return res;}int main(void) {cin.tie(0); ios_base::sync_with_stdio(false);cout << solve() << endl;return 0;}