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D.cpp
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D.cpp
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/*
Author - Silent Knight
Institution - BIT Mesra
*/
#include<bits/stdc++.h>
using namespace std;
typedef long long int ll;
typedef long double ld;
#define pb push_back
ll modInverse(ll n,ll p)
{
ll x = n;
ll y = p-2;
ll res = 1;
x = x % p;
while (y > 0)
{
if (y & 1)
res = (res*x) % p;
y = y>>1;
x = (x*x) % p;
}
return res;
}
ll nCrModPFermat(ll n,ll r,ll p) //if mod value is prime
{
if (r == 0)
return 1;
ll fac[n+1];
fac[0] = 1;
for (ll i=1 ; i<=n; i++)
fac[i] = fac[i-1]*i%p;
return (fac[n]*modInverse(fac[r], p) % p*modInverse(fac[n-r], p) % p) % p;
}
ll nCrModP(ll n,ll r,ll p) //normal iterative solution for all values of mod
{
r = min(r,n-r);
ll c[r+1];
memset(c,0,sizeof(c));
c[0] = 1;
for(ll i=1;i<=n;i++)
{
for(ll j=min(i,r);j>0;j--)
{
c[j] = (c[j] + c[j-1])%p;
}
}
return c[r];
}
void PacalCombinations(ll size)
{
ll a[size][size];
for(ll i=0;i<size;i++)
{
for(ll j=0;j<size;j++)
a[i][j] = 0;
}
a[0][0] = 1;
for(ll i=1;i<size;i++)
{
for(ll j=0;j<=i;j++)
{
if(j == 0 || j == i)
a[i][j] = 1;
else
a[i][j] = a[i-1][j-1] + a[i-1][j];
}
}
}
ll power(ll x, ll y, ll p)
{
ll res = 1;
x = x % p;
while (y > 0)
{
if (y & 1)
res = (res*x) % p;
y = y>>1;
x = (x*x) % p;
}
return res;
}
const ll N = 6e5+101;
const ll maxN = 1e17;
ll n, k;
ll cnt[N];
ll maxi[N], mini[N];
ll a[N];
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
ll t;
cin>>t;
while(t--)
{
cin>>n>>k;
for(ll i=1;i<=n;i++)
cin>>a[i];
for(ll i=1;i<=n/2;i++)
{
maxi[i] = max(a[i], a[n - i + 1]) + k;
cnt[a[i] + a[n - i + 1]] += 1;
mini[i] = min(a[i], a[n - i + 1]);
}
sort(maxi + 1, maxi + n / 2 + 1);
sort(mini + 1, mini + n / 2 + 1);
ll ans = 1e18;
for(ll i=1;i<=2*k;i++)
{
ll val = i;
ll position1 = lower_bound(maxi + 1, maxi + n / 2 + 1, val) - maxi - 1;
ll position2 = lower_bound(mini + 1, mini + n / 2 + 1, val) - mini;
position2 = n/2 - position2 + 1;
ll tmp = (position1 + position2) * 2 + (n / 2 - position1 - position2) - cnt[ val ];
ans = min(ans, tmp);
}
for(ll i=1;i<=n/2;i++)
cnt[ a[i] + a[n - i + 1] ] -= 1;
cout<<ans<<"\n";
}
}