传送门
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- 思路：
题意：
思路：
存个板子
// Problem: P5367 【模板】康托展开
// Contest: Luogu
// URL: https://www.luogu.com.cn/problem/P5367
// Memory Limit: 64 MB
// Time Limit: 1200 ms
//
// Powered by CP Editor (https://cpeditor.org)//#pragma GCC optimize("Ofast,no-stack-protector,unroll-loops,fast-math")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4.1,sse4.2,avx,avx2,popcnt,tune=native")
//#pragma GCC optimize(2)
#include<cstdio>
#include<iostream>
#include<string>
#include<cstring>
#include<map>
#include<cmath>
#include<cctype>
#include<vector>
#include<set>
#include<queue>
#include<algorithm>
#include<sstream>
#include<ctime>
#include<cstdlib>
#include<random>
#include<cassert>
#define X first
#define Y second
#define L (u<<1)
#define R (u<<1|1)
#define pb push_back
#define mk make_pair
#define Mid ((tr[u].l+tr[u].r)>>1)
#define Len(u) (tr[u].r-tr[u].l+1)
#define random(a,b) ((a)+rand()%((b)-(a)+1))
#define db puts("---")
using namespace std;//void rd_cre() { freopen("d://dp//data.txt","w",stdout); srand(time(NULL)); }
//void rd_ac() { freopen("d://dp//data.txt","r",stdin); freopen("d://dp//AC.txt","w",stdout); }
//void rd_wa() { freopen("d://dp//data.txt","r",stdin); freopen("d://dp//WA.txt","w",stdout); }typedef long long LL;
typedef unsigned long long ULL;
typedef pair<int,int> PII;const int N=1000010,mod=998244353,INF=0x3f3f3f3f;
const double eps=1e-6;int n;
int a[N];
LL fun[N];
struct Node {int l,r;int cnt;
}tr[N<<2];void pushup(int u) {tr[u].cnt=tr[L].cnt+tr[R].cnt;
}void build(int u,int l,int r) {tr[u]={l,r};if(l==r) {tr[u].cnt=1;return;}build(L,l,Mid); build(R,Mid+1,r);pushup(u);
}void change(int u,int pos) {if(tr[u].l==tr[u].r) {tr[u].cnt=0;return;}if(pos<=Mid) change(L,pos);else change(R,pos);pushup(u);
} int query(int u,int l,int r) {if(tr[u].l>=l&&tr[u].r<=r) return tr[u].cnt;int ans=0;if(l<=Mid) ans+=query(L,l,r);if(r>Mid) ans+=query(R,l,r);return ans;
}int main()
{
// ios::sync_with_stdio(false);
// cin.tie(0);scanf("%d",&n); fun[0]=1;for(int i=1;i<=n;i++) scanf("%d",&a[i]),fun[i]=fun[i-1]*i%mod;build(1,1,n);LL ans=1; for(int i=1;i<=n;i++) {int cnt=query(1,1,a[i]-1);ans+=fun[n-i]*cnt%mod; ans%=mod;change(1,a[i]);}cout<<ans<<endl;return 0;
}
/**/
