104 lines
2.3 KiB
C++
104 lines
2.3 KiB
C++
#include <stdio.h>
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#include <iostream>
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using namespace std;
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#define mod 1000000007
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#define llt long long
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llt cal[110],a[110],A[110];
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llt tree[330];
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template<class T>
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inline char read(T &n){
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T x = 0, tmp = 1; char c = getchar();
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while((c < '0' | c > '9') && c != '-' && c != EOF) c = getchar();
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if(c == '-') c = getchar(), tmp = -1;
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while(c >= '0' && c <= '9') x *= 10, x += (c - '0'),c = getchar();
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n = x*tmp;
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return c;
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}
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template <class T>
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inline void write(T n) {
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if(n < 0) {
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putchar('-');
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n = -n;
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}
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int len = 0,data[20];
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while(n) {
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data[len++] = n%10;
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n /= 10;
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}
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if(!len) data[len++] = 0;
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while(len--) putchar(data[len]+48);
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}
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void create(llt l,llt r,llt rt)
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{
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tree[rt]=0;
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if(l==r) return;
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llt mid=(l+r)>>1;
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create(l,mid,rt<<1);
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create(mid+1,r,rt<<1|1);
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}
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llt query(llt ll,llt rr,llt l,llt r,llt rt)
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{
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if(l==ll&&r==rr) return tree[rt];
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llt mid=(l+r)>>1;
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if(rr<=mid) return query(ll,rr,l,mid,rt<<1);
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else if(ll>mid) return query(ll,rr,mid+1,r,rt<<1|1);
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else
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{
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llt ans=query(ll,mid,l,mid,rt<<1);
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ans+=query(mid+1,rr,mid+1,r,rt<<1|1);
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return ans;
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}
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}
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void update(llt l,llt r,llt rt,llt x)
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{
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if(l==x&&r==x)
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{
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tree[rt]++;
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return;
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}
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llt mid=(l+r)>>1;
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if(x<=mid) update(l,mid,rt<<1,x);
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else update(mid+1,r,rt<<1|1,x);
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tree[rt]=tree[rt<<1]+tree[rt<<1|1];
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}
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void init()
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{
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cal[0]=0,cal[1]=0,cal[2]=1;
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A[1]=1;A[0]=1;
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for(int i=2;i<=100;i++)
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{A[i]=(A[i-1]*i)%mod;
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}
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for(int i=3;i<=100;i++)
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{
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cal[i]=((i*cal[i-1])%mod+(i*(i-1)*A[i-1]/2)%mod)%mod;
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}
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}
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llt sum(llt x)
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{
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return ((x-1)*x)/2;
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}
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int main()
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{
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init();llt n;
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while(scanf("%I64d",&n)!=EOF)
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{
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llt ans=0;
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llt i,j,pre=0,tmp=0;
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llt k;
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create(1,100,1);
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for(i=1;i<=n;i++)
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{
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read(a[i]);
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tmp=query(a[i]+1>100?100:a[i]+1,100,1,100,1);
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j=n-i-(n-a[i]-tmp);
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if(j<=0) continue;
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k=A[n-i];llt p=cal[n-i];
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ans=(ans+((p*j)%mod+(pre*k*j)%mod+(sum(j)*k)%mod)%mod)%mod;
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update(1,100,1,a[i]);
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pre+=j;
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}
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printf("%I64d\n",ans);
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}
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return 0;
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}
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