結果

問題 No.1300 Sum of Inversions
ユーザー kappybar
提出日時 2020-11-27 22:06:11
言語 C++14
(gcc 13.3.0 + boost 1.87.0)
結果
AC  
実行時間 175 ms / 2,000 ms
コード長 3,807 bytes
コンパイル時間 1,852 ms
コンパイル使用メモリ 177,200 KB
実行使用メモリ 15,872 KB
最終ジャッジ日時 2024-07-26 12:53:56
合計ジャッジ時間 7,519 ms
ジャッジサーバーID
（参考情報） 		judge2 / judge1
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 * 34
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 <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define chmin(x,y) x = min((x),(y));
#define chmax(x,y) x = max((x),(y));
using namespace std;
using ll = long long ;
using P = pair<int,int> ;
using pll = pair<long long,long long>;
const int INF = 1e9;
const long long LINF = 1e17;
//const int MOD = 1000000007;
const int MOD = 998244353;
const double PI = 3.14159265358979323846;
template<int mod> struct ModInt{
    long long x=0; 
    constexpr ModInt(long long x=0):x((x%mod+mod)%mod){}
    constexpr ModInt operator+(const ModInt& r)const{return ModInt(*this)+=r;}
    constexpr ModInt operator-(const ModInt& r)const{return ModInt(*this)-=r;}
    constexpr ModInt operator*(const ModInt& r)const{return ModInt(*this)*=r;}
    constexpr ModInt operator/(const ModInt& r)const{return ModInt(*this)/=r;}
    constexpr ModInt& operator+=(const ModInt& r){ if((x+=r.x)>=mod) x-=mod; return *this;}
    constexpr ModInt& operator-=(const ModInt& r){ if((x-=r.x)<0) x+=mod; return *this;}
    constexpr ModInt& operator*=(const ModInt& r){ if((x*=r.x)>=mod) x%=mod; return *this;}
    constexpr ModInt& operator/=(const ModInt& r){ return *this*=r.inv();}
    ModInt inv() const {
        long long s=x,sx=1,sy=0,t=mod,tx=0,ty=1;
        while(s%t!=0){
            long long temp=s/t,u=s-t*temp,ux=sx-temp*tx,uy=sy-temp*ty;
            s=t;sx=tx;sy=ty;
            t=u;tx=ux;ty=uy;
        }
        return ModInt(tx);
    }
    ModInt pow(long long n) const {
        ModInt a=1;
        ModInt b=*this;
        while(n>0){
            if(n&1) a*=b;
            b*=b;
            n>>=1;
        }
        return a;
    }
    friend constexpr ostream& operator<<(ostream& os,const ModInt<mod>& a) {return os << a.x;}
    friend constexpr istream& operator>>(istream& is,ModInt<mod>& a) {return is >> a.x;}
};
using mint = ModInt<MOD>;
//1-indexedに注意！！！
struct BIT{
    private:
    int n,n_;
    vector<long long> bit;
    public:
    BIT(int n):n(n){
        bit.resize(n+1);
        n_ = 1;
        while(n_<=n) n_<<=1;
        n_ >>= 1;
    }
    //1-index
    long long sum(int i){
        long long res = 0;
        while(i > 0){
            res += bit[i];
            i -= i&-i;
        }
        return res;
    }
    //1-index
    void add(int i,long long val){
        while(i <= n){
            bit[i] += val;
            i += i&-i;
        }
    }
    //return 1-index
    int lowerbound(long long w){
        if(w <= 0) return 0;
        int x = 0;
        for(int k=n_;k>0;k>>=1){
            if(x+k<=n&&bit[x+k]<w){
                w -= bit[x+k];
                x += k;
            }
        }
        return x+1;
    }
};
template<typename T>
vector<T> compress(vector<T> &a){
    vector<T> val = a;
    int n = (int)a.size();
    sort(val.begin(),val.end());
    val.erase(unique(val.begin(),val.end()),val.end());
    for(int i=0;i<n;i++){
        a[i] = lower_bound(val.begin(),val.end(),a[i]) - val.begin();
    }
    return val;
}
int main(){
    int n;
    cin >> n;
    vector<ll> a(n);
    vector<ll> b(n),c(n);
    rep(i,n) cin >> a[i];
    vector<ll> mp = compress(a);
    BIT bit(n);
    rep(i,n){
        b[i] = i - bit.sum(a[i]+1);
        bit.add(a[i]+1,1);
    }
    BIT bb(n);
    rep(i,n){
        c[n-i-1] = bb.sum(a[n-i-1]-1+1);
        bb.add(a[n-i-1]+1,1);
    }
    mint ans = 0;
    rep(i,n){
        ans += mint(b[i]) * mint(c[i]) * mint(mp[a[i]]);
    }
    BIT bitsum(n);
    mint cum = 0;
    rep(i,n){
        ans += mint(c[i]) * (cum - mint(bitsum.sum(a[i]+1)));
        bitsum.add(a[i]+1,mp[a[i]]);
        cum += mp[a[i]];
    }
    BIT bbsum(n);
    rep(i,n){
        ans += mint(b[n-1-i]) * mint(bbsum.sum(a[n-i-1]-1+1));
        bbsum.add(a[n-i-1]+1,mp[a[n-i-1]]);
    }
    cout << ans << endl;
    return 0;
}
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