description: You have a permutation: an array a = [a_1, a_2, …, a_n] of distinct integers from 1 to n. The length of the permutation n is odd.
  
  You need to sort the permutation in increasing order.
  
  In one step, you can choose any prefix of the permutation with an odd length and reverse it. Formally, if a = [a_1, a_2, …, a_n], you can choose any odd integer p between 1 and n, inclusive, and set a to [a_p, a_{p-1}, …, a_1, a_{p+1}, a_{p+2}, …, a_n].
  
  Find a way to sort a using no more than 5n/2 reversals of the above kind, or determine that such a way doesn't exist. The number of reversals doesn't have to be minimized.
  
  Input
  
  Each test contains multiple test cases. The first line contains the number of test cases t (1 ≤ t ≤ 100). Description of the test cases follows.
  
  The first line of each test case contains a single integer n (3 ≤ n ≤ 2021; n is odd) — the length of the permutation.
  
  The second line contains n distinct integers a_1, a_2, …, a_n (1 ≤ a_i ≤ n) — the permutation itself. 
  
  It is guaranteed that the sum of n over all test cases does not exceed 2021.
  
  Output
  
  For each test case, if it's impossible to sort the given permutation in at most 5n/2 reversals, print a single integer -1.
  
  Otherwise, print an integer m (0 ≤ m ≤ 5n/2), denoting the number of reversals in your sequence of steps, followed by m integers p_i (1 ≤ p_i ≤ n; p_i is odd), denoting the lengths of the prefixes of a to be reversed, in chronological order.
  
  Note that m doesn't have to be minimized. If there are multiple answers, print any.
  
  Example
  
  Input
  
  
  3
  3
  1 2 3
  5
  3 4 5 2 1
  3
  2 1 3
  
  
  Output
  
  
  4
  3 3 3 3
  2
  3 5
  -1
  
  Note
  
  In the first test case, the permutation is already sorted. Any even number of reversals of the length 3 prefix doesn't change that fact.
  
  In the second test case, after reversing the prefix of length 3 the permutation will change to [5, 4, 3, 2, 1], and then after reversing the prefix of length 5 the permutation will change to [1, 2, 3, 4, 5].
  
  In the third test case, it's impossible to sort the permutation.
solution: import java.io.OutputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.OutputStream;
  import java.util.Arrays;
  import java.io.IOException;
  import java.lang.reflect.Field;
  import java.nio.charset.StandardCharsets;
  import java.io.UncheckedIOException;
  import java.io.Closeable;
  import java.io.InputStream;
  
  /**
   * Built using CHelper plug-in
   * Actual solution is at the top
   */
  public class Main {
      public static void main(String[] args) throws Exception {
          Thread thread = new Thread(null, new TaskAdapter(), "", 1 << 29);
          thread.start();
          thread.join();
      }
  
      static class TaskAdapter implements Runnable {
          @Override
          public void run() {
              InputStream inputStream = System.in;
              OutputStream outputStream = System.out;
              FastInput in = new FastInput(inputStream);
              FastOutput out = new FastOutput(outputStream);
              CBottomTierReversals solver = new CBottomTierReversals();
              int testCount = Integer.parseInt(in.next());
              for (int i = 1; i <= testCount; i++)
                  solver.solve(i, in, out);
              out.close();
          }
      }
  
      static class CBottomTierReversals {
          int[] data;
          int[] indices;
          IntegerArrayList sol;
  
          public void solve(int testNumber, FastInput in, FastOutput out) {
              int n = in.ri();
              data = in.ri(n);
              indices = new int[n];
              sol = new IntegerArrayList(5 * n);
              for (int i = 0; i < n; i++) {
                  data[i]--;
                  if (data[i] % 2 != i % 2) {
                      out.println(-1);
                      return;
                  }
                  indices[data[i]] = i;
              }
              for (int i = n - 1; i >= 1; i -= 2) {
                  int a = i;
                  int b = i - 1;
                  add(indices[a] + 1);
                  add(indices[b]);
                  add(indices[b] + 2);
                  add(indices[a] + 1);
                  add(i + 1);
                  assert indices[a] == a;
                  assert indices[b] == b;
              }
              for (int i = 0; i < n; i++) {
                  assert data[i] == i;
              }
              out.println(sol.size());
              for (int x : sol.toArray()) {
                  out.append(x).append(' ');
              }
              out.println();
          }
  
          public void swap(int i, int j) {
              int tmp = data[i];
              data[i] = data[j];
              data[j] = tmp;
              indices[data[i]] = i;
              indices[data[j]] = j;
          }
  
          public void add(int k) {
              assert k % 2 == 1;
              int l = 0;
              int r = k - 1;
              while (l < r) {
                  swap(l, r);
                  l++;
                  r--;
              }
              sol.add(k);
          }
  
      }
  
      static class FastOutput implements AutoCloseable, Closeable, Appendable {
          private static final int THRESHOLD = 32 << 10;
          private OutputStream writer;
          private StringBuilder cache = new StringBuilder(THRESHOLD * 2);
          private static Field stringBuilderValueField;
          private char[] charBuf = new char[THRESHOLD * 2];
          private byte[] byteBuf = new byte[THRESHOLD * 2];
  
          static {
              try {
                  stringBuilderValueField = StringBuilder.class.getSuperclass().getDeclaredField("value");
                  stringBuilderValueField.setAccessible(true);
              } catch (Exception e) {
                  stringBuilderValueField = null;
              }
              stringBuilderValueField = null;
          }
  
          public FastOutput append(CharSequence csq) {
              cache.append(csq);
              return this;
          }
  
          public FastOutput append(CharSequence csq, int start, int end) {
              cache.append(csq, start, end);
              return this;
          }
  
          private void afterWrite() {
              if (cache.length() < THRESHOLD) {
                  return;
              }
              flush();
          }
  
          public FastOutput(OutputStream writer) {
              this.writer = writer;
          }
  
          public FastOutput append(char c) {
              cache.append(c);
              afterWrite();
              return this;
          }
  
          public FastOutput append(int c) {
              cache.append(c);
              afterWrite();
              return this;
          }
  
          public FastOutput println(int c) {
              return append(c).println();
          }
  
          public FastOutput println() {
              return append('\n');
          }
  
          public FastOutput flush() {
              try {
                  if (stringBuilderValueField != null) {
                      try {
                          byte[] value = (byte[]) stringBuilderValueField.get(cache);
                          writer.write(value, 0, cache.length());
                      } catch (Exception e) {
                          stringBuilderValueField = null;
                      }
                  }
                  if (stringBuilderValueField == null) {
                      int n = cache.length();
                      if (n > byteBuf.length) {
                          //slow
                          writer.write(cache.toString().getBytes(StandardCharsets.UTF_8));
  //                writer.append(cache);
                      } else {
                          cache.getChars(0, n, charBuf, 0);
                          for (int i = 0; i < n; i++) {
                              byteBuf[i] = (byte) charBuf[i];
                          }
                          writer.write(byteBuf, 0, n);
                      }
                  }
                  writer.flush();
                  cache.setLength(0);
              } catch (IOException e) {
                  throw new UncheckedIOException(e);
              }
              return this;
          }
  
          public void close() {
              flush();
              try {
                  writer.close();
              } catch (IOException e) {
                  throw new UncheckedIOException(e);
              }
          }
  
          public String toString() {
              return cache.toString();
          }
  
      }
  
      static class SequenceUtils {
          public static boolean equal(int[] a, int al, int ar, int[] b, int bl, int br) {
              if ((ar - al) != (br - bl)) {
                  return false;
              }
              for (int i = al, j = bl; i <= ar; i++, j++) {
                  if (a[i] != b[j]) {
                      return false;
                  }
              }
              return true;
          }
  
      }
  
      static class IntegerArrayList implements Cloneable {
          private int size;
          private int cap;
          private int[] data;
          private static final int[] EMPTY = new int[0];
  
          public IntegerArrayList(int cap) {
              this.cap = cap;
              if (cap == 0) {
                  data = EMPTY;
              } else {
                  data = new int[cap];
              }
          }
  
          public IntegerArrayList(int[] data) {
              this(0);
              addAll(data);
          }
  
          public IntegerArrayList(IntegerArrayList list) {
              this.size = list.size;
              this.cap = list.cap;
              this.data = Arrays.copyOf(list.data, size);
          }
  
          public IntegerArrayList() {
              this(0);
          }
  
          public void ensureSpace(int req) {
              if (req > cap) {
                  while (cap < req) {
                      cap = Math.max(cap + 10, 2 * cap);
                  }
                  data = Arrays.copyOf(data, cap);
              }
          }
  
          public void add(int x) {
              ensureSpace(size + 1);
              data[size++] = x;
          }
  
          public void addAll(int[] x) {
              addAll(x, 0, x.length);
          }
  
          public void addAll(int[] x, int offset, int len) {
              ensureSpace(size + len);
              System.arraycopy(x, offset, data, size, len);
              size += len;
          }
  
          public void addAll(IntegerArrayList list) {
              addAll(list.data, 0, list.size);
          }
  
          public int size() {
              return size;
          }
  
          public int[] toArray() {
              return Arrays.copyOf(data, size);
          }
  
          public String toString() {
              return Arrays.toString(toArray());
          }
  
          public boolean equals(Object obj) {
              if (!(obj instanceof IntegerArrayList)) {
                  return false;
              }
              IntegerArrayList other = (IntegerArrayList) obj;
              return SequenceUtils.equal(data, 0, size - 1, other.data, 0, other.size - 1);
          }
  
          public int hashCode() {
              int h = 1;
              for (int i = 0; i < size; i++) {
                  h = h * 31 + Integer.hashCode(data[i]);
              }
              return h;
          }
  
          public IntegerArrayList clone() {
              IntegerArrayList ans = new IntegerArrayList();
              ans.addAll(this);
              return ans;
          }
  
      }
  
      static class FastInput {
          private final InputStream is;
          private StringBuilder defaultStringBuf = new StringBuilder(1 << 13);
          private byte[] buf = new byte[1 << 13];
          private int bufLen;
          private int bufOffset;
          private int next;
  
          public FastInput(InputStream is) {
              this.is = is;
          }
  
          public void populate(int[] data) {
              for (int i = 0; i < data.length; i++) {
                  data[i] = readInt();
              }
          }
  
          private int read() {
              while (bufLen == bufOffset) {
                  bufOffset = 0;
                  try {
                      bufLen = is.read(buf);
                  } catch (IOException e) {
                      bufLen = -1;
                  }
                  if (bufLen == -1) {
                      return -1;
                  }
              }
              return buf[bufOffset++];
          }
  
          public void skipBlank() {
              while (next >= 0 && next <= 32) {
                  next = read();
              }
          }
  
          public String next() {
              return readString();
          }
  
          public int ri() {
              return readInt();
          }
  
          public int[] ri(int n) {
              int[] ans = new int[n];
              populate(ans);
              return ans;
          }
  
          public int readInt() {
              boolean rev = false;
  
              skipBlank();
              if (next == '+' || next == '-') {
                  rev = next == '-';
                  next = read();
              }
  
              int val = 0;
              while (next >= '0' && next <= '9') {
                  val = val * 10 - next + '0';
                  next = read();
              }
  
              return rev ? val : -val;
          }
  
          public String readString(StringBuilder builder) {
              skipBlank();
  
              while (next > 32) {
                  builder.append((char) next);
                  next = read();
              }
  
              return builder.toString();
          }
  
          public String readString() {
              defaultStringBuf.setLength(0);
              return readString(defaultStringBuf);
          }
  
      }
  }
  
  