C. The third problem

C. The Third Problem( Looking for a regular )

You can find $0,1$ The position of the cannot be changed .

And then there's watching $2$.

Might as well set $p_0<p_1$

if $p_2<p_0$ or $p_2>p_1$ , be $p_2$ Position cannot be changed .

because $[p_2,p_1]$ or $[p_0,p_2]$ Will receive $p_2$ Location affects .

So only $p_0<p_2<p_1$ Satisfy .

$p_2$ The optional cases are ：$p_1-p_0+1-2$

about $p_3$ If it is not within the range of these three numbers, it is also fixed .

Otherwise, it can be any one in the range $r-l+1-3$
Therefore, direct simulation is sufficient .

#include<bits/stdc++.h>

using namespace std;
typedef long long ll;

const ll NMAX=1e5+5,MOD=1e9+7;

ll v[NMAX],pos[NMAX];
void tc(){
    

    ll n,l,r,ans=1;

    cin>>n;

    for(ll i=0;i<n;i++){
    
        cin>>v[i];
        pos[v[i]]=i;
    }

    l = r = pos[0];

    for(ll i=1;i<n;i++){
    
        if(pos[i]<l) l = pos[i];

        else if(pos[i]>r) r = pos[i];

        else ans=ans*(r-l+1-i)%MOD;
    }
    cout<<ans<<'\n';
}
int main()
{
    
    ios_base::sync_with_stdio(false); cin.tie(0);
    ll t;
    cin>>t;
    while(t--)
        tc();
    return 0;
}