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(int[] P) {
  const N = cast(int)(P.length);
  
  int[] cuts;
  cuts ~= -1;
  foreach (i; 0 .. N) if (P[i] == i) {
    cuts ~= i;
  }
  cuts ~= N;
  const len = cast(int)(cuts.length) - 1;
  
  auto ps = P.dup;
  foreach (j; 0 .. len) {
    ps[cuts[j] + 1 .. cuts[j + 1]].sort;
  }
  foreach (i; 0 .. N) {
    if (ps[i] != i) {
      return [-1];
    }
  }
  
  ps = P.dup;
  int[] ans;
  void oper(int i) {
    assert(0 <= i); assert(i < N - 1);
    assert(ps[i] != i);
    assert(ps[i + 1] != i + 1);
    swap(ps[i], ps[i + 1]);
    ans ~= i;
  }
  
  auto ls = new int[N + 1];
  auto rs = new int[N + 1];
  void update() {
    ls[0] = -1;
    foreach (i; 0 .. N) {
      ls[i + 1] = max(ls[i], ps[i]);
    }
    rs[N] = N;
    foreach_reverse (i; 0 .. N) {
      rs[i] = min(ps[i], rs[i + 1]);
    }
  }
  update();
  
  bool isGood(int i) {
    const a = ps[i];
    const b = ps[i + 1];
    bool ret = true;
    ret = ret && (a != i);
    ret = ret && (b != i + 1);
    if (a == i + 1) {
      if (b == i) {
        ret = ret && (ls[i] < b && a < rs[i + 2]);
      } else {
        ret = ret && (ls[i] < a && a < rs[i + 2]);
      }
    } else {
      if (b == i) {
        ret = ret && (ls[i] < b && b < rs[i + 2]);
      } else {
        //
      }
    }
    return ret;
  }
  
  foreach (x; 0 .. N) {
    int pos;
    foreach (i; 0 .. N) {
      if (ps[i] == x) {
        pos = i;
        break;
      }
    }
    void go(int i) {
      if (!isGood(i)) {
        go(i - 1);
      }
      assert(isGood(i));
      oper(i);
      update();
    }
    foreach_reverse (i; x .. pos) {
      go(i);
    }
  }
  
  for (; ; ) {
    bool upd;
    foreach (i; 0 .. N - 1) {
      
    }
    if (!upd) {
      break;
    }
  }
  
  foreach (i; 0 .. N) {
    assert(ps[i] == i, format("%s: %s %s", P, ans, ps));
  }
  return ans;
}

void main() {
  debug {
    foreach (n; 1 .. 6 + 1) {
      DList!(int[]) que;
      bool[string] vis;
      auto start = iota(n).array;
      vis[start.to!string] = true;
      que ~= start;
      for (; !que.empty; ) {
        auto ps = que.front;
        que.removeFront;
        foreach (i; 0 .. n - 1) {
          if (ps[i + 1] != i && ps[i] != i + 1) {
            auto qs = ps.dup;
            swap(qs[i], qs[i + 1]);
            const key = qs.to!string;
            if (key !in vis) {
              vis[key] = true;
              que ~= qs;
            }
          }
        }
      }
      int cnt;
      auto perm = iota(n).array;
      do {
        const res = solve(perm);
        if (perm.to!string in vis) {
          assert(res != [-1]);
        } else {
          assert(res == [-1]);
          ++cnt;
          writeln(perm);
          
          int[] cuts;
          cuts ~= -1;
          foreach (i; 0 .. n) if (perm[i] == i) cuts ~= i;
          cuts ~= n;
          auto ps = perm.dup;
          foreach (j; 0 .. cast(int)(cuts.length) - 1) {
            ps[cuts[j] + 1 .. cuts[j + 1]].sort;
          }
          bool good = true;
          foreach (i; 0 .. n) good = good && (ps[i] == i);
          assert(!good);
        }
      } while (perm.nextPermutation);
      writeln(n, ": ", cnt);
    }
  }
  
  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) {
  }
}