import std.conv, std.functional, std.range, std.stdio, std.string;
import std.algorithm, std.array, std.bigint, std.bitmanip, std.complex, std.container, std.math, std.mathspecial, std.numeric, std.regex, std.typecons;
import core.bitop;

class EOFException : Throwable { this() { super("EOF"); } }
string[] tokens;
string readToken() { for (; tokens.empty; ) { if (stdin.eof) { throw new EOFException; } tokens = readln.split; } auto token = tokens.front; tokens.popFront; return token; }
int readInt() { return readToken.to!int; }
long readLong() { return readToken.to!long; }
real readReal() { return readToken.to!real; }

bool chmin(T)(ref T t, in T f) { if (t > f) { t = f; return true; } else { return false; } }
bool chmax(T)(ref T t, in T f) { if (t < f) { t = f; return true; } else { return false; } }

int binarySearch(alias pred, T)(in T[] as) { int lo = -1, hi = cast(int)(as.length); for (; lo + 1 < hi; ) { const mid = (lo + hi) >> 1; (unaryFun!pred(as[mid]) ? hi : lo) = mid; } return hi; }
int lowerBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a >= val)); }
int upperBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a > val)); }


int[] solve(const(int[]) P) {
  const N = cast(int)(P.length);
  
  int[] cuts;
  cuts ~= -1;
  foreach (i; 0 .. N) if (P[i] == i) {
    cuts ~= i;
  }
  const len = cast(int)(cuts.length);
  cuts ~= N;
  foreach (j; 0 .. len) {
    const l = cuts[j] + 1;
    const r = cuts[j + 1];
    foreach (i; l .. r) {
      if (!(l <= P[i] && P[i] < r)) {
        return [-1];
      }
    }
  }
  
  auto ps = P.dup;
  int[] ans;
  void oper(int i) {
    bool ok = true;
    ok = ok && (0 <= i && i < N - 1);
    ok = ok && (ps[i] != i);
    ok = ok && (ps[i + 1] != i + 1);
    assert(ok, format("%s: %s %s", P, ps, i));
    swap(ps[i], ps[i + 1]);
    ans ~= i;
  }
  
  foreach (j; 0 .. len) {
    const l = cuts[j] + 1;
    const r = cuts[j + 1];
    foreach (_; 0 .. r - l - 1) {
      foreach (i; l .. r - 1) {
        if (ps[i] < i && ps[i + 1] > i + 1) {
          oper(i);
        }
      }
    }
    // >>><<<
    foreach (_; 0 .. r - l + 1) {
      foreach (i; l .. r - 1) {
        if (ps[i] > i && ps[i + 1] > i + 1 && ps[i] > ps[i + 1]) {
          oper(i);
        }
        if (ps[i] < i && ps[i + 1] < i + 1 && ps[i] > ps[i + 1]) {
          oper(i);
        }
      }
    }
    foreach (x; l .. r) {
      int pos;
      foreach (i; l .. r) {
        if (ps[i] == x) {
          pos = i;
          break;
        }
      }
      foreach_reverse (i; x .. pos) {
        oper(i);
      }
    }
  }
  
  foreach (i; 0 .. N) {
    assert(ps[i] == i);
  }
  return ans;
}

void main() {
  try {
    for (; ; ) {
      const numCases = readInt;
      foreach (caseId; 0 .. numCases) {
        const N = readInt;
        auto P = new int[N];
        foreach (i; 0 .. N) {
          P[i] = readInt - 1;
        }
        
        const ans = solve(P);
        if (ans == [-1]) {
          writeln(-1);
        } else {
          writeln(ans.length);
          foreach (index, i; ans) {
            if (index) write(" ");
            write(i + 1);
          }
          writeln;
        }
      }
    }
  } catch (EOFException e) {
  }
}