#include <bits/stdc++.h>
#define ll long long
#define db long double
#define II pair <ll,ll>
#define III pair <ll,II>
#define IV pair <vector <int>,vector <int> >
#define TII pair <treap*,treap*>
#define fst first
#define snd second
#define BIT(x,i) ((x>>i)&1)
#define pi acos(-1)
#define to_radian(x) (x*pi/180.0)
#define to_degree(x) (x*180.0/pi)
#define Log(x) (31-__builtin_clz((int)x))
#define LogLL(x) (63-__builtin_clzll((ll)x))
//#include "gondola.h"
using namespace std;
int n,i,a[250005];
int valid(int n,int a[])
{
int last_u=0,last_i=0;
map <int,int> d;
for(i=0;i<n;i++)
{
int u=a[i];
if(d[u]) return 0;
d[u]=1;
if(u>n) continue;
if(last_u>0 && (u-last_u+n)%n!=(i-last_i+n)%n)
return 0;
last_u=u; last_i=i;
}
return 1;
}
int m,res[250005],pos[250005],last[250005];
int replacement(int n,int a[], int res[])
{
int ma=0,m=0;
memset(last,-1,sizeof(last));
for(i=0;i<n;i++) ma=max(ma,a[i]),last[a[i]]=i;
for(i=1;i<=n;i++)
if(last[i]>-1) break;
if(i>n)
{
for(i=0;i<n;i++) a[i]=i+1;
}
else
{
// cerr<<i<<" "<<last[i]<<'\n';
int u=i,pos=last[i];
a[pos]=i;
for(i=pos+1;i<n;i++)
{
if(u==n) u=1; else u++;
a[i]=u;
}
u=a[pos];
for(i=pos-1;i>=0;i--)
{
if(u==1) u=n; else u--;
a[i]=u;
}
}
for(i=0;i<n;i++) pos[a[i]]=i;
set <int> Replace;
for(i=1;i<=n;i++)
if(last[i]==-1) Replace.insert(i);
for(i=n+1;i<=ma;i++)
if(last[i]==-1)
{
int u=*Replace.begin(); Replace.erase(u);
a[pos[u]]=i; pos[i]=pos[u];
Replace.insert(i);
res[m++]=u;
}
else
{
int u=a[last[i]]; Replace.erase(u);
a[pos[u]]=i; pos[i]=pos[u];
res[m++]=u;
}
return m;
}
const ll mod=round(1e9)+9;
ll lt(ll a,ll b)
{
if(b==0) return 1;
ll tg=lt(a,b/2);
return (b%2==0) ? tg*tg%mod : tg*tg%mod*a%mod;
}
int countReplacement(int n,int a[])
{
if(!valid(n,a)) return 0;
vector <int> val;
for(i=0;i<n;i++)
if(a[i]>n) val.push_back(a[i]);
int last=n,left=val.size();
ll res=1;
if(left==n) res=n;
sort(val.begin(),val.end());
for(int x:val)
{
res=res*lt(left,x-last-1)%mod;
last=x; left--;
}
return res;
}
/*
int main()
{
freopen("gondola.inp","r",stdin);
freopen("gondola.out","w",stdout);
cin>>n;
for(i=0;i<n;i++) cin>>a[i];
cout<<countReplacement(n,a);
}
*/
Compilation message
/usr/bin/ld: /tmp/cce41auQ.o: in function `main':
grader.cpp:(.text.startup+0xb6): undefined reference to `valid'
/usr/bin/ld: grader.cpp:(.text.startup+0x108): undefined reference to `countReplacement'
/usr/bin/ld: grader.cpp:(.text.startup+0x132): undefined reference to `replacement'
collect2: error: ld returned 1 exit status
