luogu_P5367 【模板】康托展开

#include<cstdio>
#define R register
typedef long long ll;
using namespace std;
const int mod=998244353;
int n,a[1001000],c[1001000];
inline void add(int x){
    for(;x<=n;x+=x&-x) c[x]++;
}
inline int ask(int x){
    int to=0;
    for(;x;x-=x&-x) to+=c[x];
    return to;
}
ll rev[1001000],ans;
inline int abc(int x){
    if(x<0) return ~x+1;
    return x;
}
int main (){
    scanf("%d",&n);
    rev[0]=1;
    for(R int i=1;i<=n;i++){
        scanf("%d",&a[i]);
        rev[i]=(rev[i-1]*i)%mod;
    }
    for(R int i=1;i<=n;i++){
        add(a[i]);
        ans=(ans+1ll*(a[i]-ask(a[i]))*rev[n-i])%mod;
    }
    printf("%lld\n",(ans+1)%mod);
    return 0;
}