description: This is an interactive problem. The only difference between the easy and hard version is the limit on number of questions.
  
  There are n players labelled from 1 to n. It is guaranteed that n is a multiple of 3.
  
  Among them, there are k impostors and n-k crewmates. The number of impostors, k, is not given to you. It is guaranteed that n/3 < k < 2n/3.
  
  In each question, you can choose three distinct integers a, b, c (1 ≤ a, b, c ≤ n) and ask: "Among the players labelled a, b and c, are there more impostors or more crewmates?" You will be given the integer 0 if there are more impostors than crewmates, and 1 otherwise.
  
  Find the number of impostors k and the indices of players that are impostors after asking at most n+6 questions.
  
  The jury is adaptive, which means the indices of impostors may not be fixed beforehand and can depend on your questions. It is guaranteed that there is at least one set of impostors which fulfills the constraints and the answers to your questions at any time.
  
  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 and only line of each test case contains a single integer n (6 ≤ n < 10^4, n is a multiple of 3) — the number of players.
  
  It is guaranteed that the sum of n over all test cases does not exceed 2 ⋅ 10^4.
  
  Interaction
  
  For each test case, the interaction starts with reading n.
  
  Then you are allowed to make at most n+6 questions in the following way:
  
  "? a b c" (1 ≤ a, b, c ≤ n, a, b and c are pairwise distinct).
  
  After each one, you should read an integer r, which is equal to 0 if there are more impostors than crewmates among players labelled a, b and c, and equal to 1 otherwise.
  
  Answer -1 instead of 0 or 1 means that you made an invalid query. Exit immediately after receiving -1 and you will see Wrong answer verdict. Otherwise you can get an arbitrary verdict because your solution will continue to read from a closed stream.
  
  When you have found the indices of all impostors, print a single line "! " (without quotes), followed by the number of impostors k, followed by k integers representing the indices of the impostors. Please note that you must print all this information on the same line. 
  
  After printing the answer, your program must then continue to solve the remaining test cases, or exit if all test cases have been solved.
  
  After printing the queries and answers do not forget to output end of line and flush the output buffer. Otherwise, you will get the Idleness limit exceeded verdict. To do flush use:
  
    * fflush(stdout) or cout.flush() in C++; 
    * System.out.flush() in Java; 
    * flush(output) in Pascal; 
    * stdout.flush() in Python; 
    * Read documentation for other languages. 
  
  
  
  Hacks
  
  You cannot make hacks in this problem.
  
  Example
  
  Input
  
  
  2
  6
  
  0
  
  1
  
  9
  
  1
  
  Output
  
  
  ? 1 2 3
  
  ? 3 4 5
  
  ! 3 4 1 2
  
  ? 7 1 9
  
  ! 4 2 3 6 8
  
  Note
  
  Explanation for example interaction (note that this example only exists to demonstrate the interaction procedure and does not provide any hint for the solution):
  
  For the first test case:
  
  Question "? 1 2 3" returns 0, so there are more impostors than crewmates among players 1, 2 and 3.
  
  Question "? 3 4 5" returns 1, so there are more crewmates than impostors among players 3, 4 and 5.
  
  Outputting "! 3 4 1 2" means that one has found all the impostors, by some miracle. There are k = 3 impostors. The players who are impostors are players 4, 1 and 2.
  
  For the second test case:
  
  Question "? 7 1 9" returns 1, so there are more crewmates than impostors among players 7, 1 and 9.
  
  Outputting "! 4 2 3 6 8" means that one has found all the impostors, by some miracle. There are k = 4 impostors. The players who are impostors are players 2, 3, 6 and 8.
solution: import java.io.*;
  import java.util.*;
  
  import static java.lang.Math.*;
  import static java.util.Arrays.*;
  
  public class cf1617d2 {
  
      public static void main(String[] args) throws IOException {
          int t = ri();
          next: while (t --> 0) {
              int n = ri(), zero = -1, one = -1, qp3[] = new int[n];
              for (int i = 0; i < n; i += 3) {
                  qp3[i] = qp3[i + 1] = qp3[i + 2] = qry(i, i + 1, i + 2);
                  if (qp3[i] == 0) {
                      zero = i;
                  } else {
                      one = i;
                  }
              }
              int qa0 = qry(zero, zero + 1, one), qb0 = qry(zero, zero + 1, one + 1);
              int qa1 = qry(one, one + 1, zero), qb1 = qry(one, one + 1, zero + 1);
              int zp, op;
              if (qa0 == 0 && qb0 == 0) {
                  zp = zero;
              } else {
                  zp = zero + 2;
              }
              if (qa1 == 1 && qb1 == 1) {
                  op = one;
              } else {
                  op = one + 2;
              }
              int a[] = new int[n];
              fill(a, -1);
              List<Integer> ans = new ArrayList<>();
              for (int i = 0; i < n; i += 3) {
                  if (qp3[i] == 0) {
                      int ql = qry(i, i + 1, op), qr = qry(i + 1, i + 2, op);
                      if (ql == 0 && qr == 0) {
                          a[i] = a[i + 1] = a[i + 2] = 0;
                      } else if (ql == 0 && qr == 1) {
                          a[i] = a[i + 1] = 0;
                          a[i + 2] = 1;
                      } else if (ql == 1 && qr == 0) {
                          a[i] = 1;
                          a[i + 1] = a[i + 2] = 0;
                      } else {
                          a[i] = a[i + 2] = 0;
                          a[i + 1] = 1;
                      }
                  } else {
                      int ql = qry(i, i + 1, zp), qr = qry(i + 1, i + 2, zp);
                      if (ql == 1 && qr == 1) {
                          a[i] = a[i + 1] = a[i + 2] = 1;
                      } else if (ql == 1 && qr == 0) {
                          a[i] = a[i + 1] = 1;
                          a[i + 2] = 0;
                      } else if (ql == 0 && qr == 1) {
                          a[i] = 0;
                          a[i + 1] = a[i + 2] = 1;
                      } else {
                          a[i] = a[i + 2] = 1;
                          a[i + 1] = 0;
                      }
                  }
                  for (int j = 0; j < 3; ++j) {
                      if (a[i + j] == 0) {
                          ans.add(i + j + 1);
                      }
                  }
              }
              ans(ans);
          }
          close();
      }
  
      static int qry(int i, int j, int k) throws IOException {
          pr("? ");
          prln(i + 1, j + 1, k + 1);
          flush();
          return ri();
      }
  
      static void ans(List<Integer> ans) {
          pr("! ");
          pr(ans.size());
          pr(' ');
          prln(ans);
          flush();
      }
  
      static BufferedReader __i = new BufferedReader(new InputStreamReader(System.in));
      static PrintWriter __o = new PrintWriter(new OutputStreamWriter(System.out));
      static StringTokenizer input;
      static Random __r = new Random();
  
      // references
      // IBIG = 1e9 + 7
      // IMAX ~= 2e9
      // LMAX ~= 9e18
  
      // constants
      static final int IBIG = 1000000007;
      static final int IMAX = 2147483647;
      static final long LMAX = 9223372036854775807L;
      // math util
      static int minof(int a, int b, int c) {return min(a, min(b, c));}
      static int minof(int... x) {if (x.length == 1) return x[0]; if (x.length == 2) return min(x[0], x[1]); if (x.length == 3) return min(x[0], min(x[1], x[2])); int min = x[0]; for (int i = 1; i < x.length; ++i) if (x[i] < min) min = x[i]; return min;}
      static long minof(long a, long b, long c) {return min(a, min(b, c));}
      static long minof(long... x) {if (x.length == 1) return x[0]; if (x.length == 2) return min(x[0], x[1]); if (x.length == 3) return min(x[0], min(x[1], x[2])); long min = x[0]; for (int i = 1; i < x.length; ++i) if (x[i] < min) min = x[i]; return min;}
      static int maxof(int a, int b, int c) {return max(a, max(b, c));}
      static int maxof(int... x) {if (x.length == 1) return x[0]; if (x.length == 2) return max(x[0], x[1]); if (x.length == 3) return max(x[0], max(x[1], x[2])); int max = x[0]; for (int i = 1; i < x.length; ++i) if (x[i] > max) max = x[i]; return max;}
      static long maxof(long a, long b, long c) {return max(a, max(b, c));}
      static long maxof(long... x) {if (x.length == 1) return x[0]; if (x.length == 2) return max(x[0], x[1]); if (x.length == 3) return max(x[0], max(x[1], x[2])); long max = x[0]; for (int i = 1; i < x.length; ++i) if (x[i] > max) max = x[i]; return max;}
      static int powi(int a, int b) {if (a == 0) return 0; int ans = 1; while (b > 0) {if ((b & 1) > 0) ans *= a; a *= a; b >>= 1;} return ans;}
      static long powl(long a, int b) {if (a == 0) return 0; long ans = 1; while (b > 0) {if ((b & 1) > 0) ans *= a; a *= a; b >>= 1;} return ans;}
      static int fli(double d) {return (int) d;}
      static int cei(double d) {return (int) ceil(d);}
      static long fll(double d) {return (long) d;}
      static long cel(double d) {return (long) ceil(d);}
      static int gcd(int a, int b) {return b == 0 ? a : gcd(b, a % b);}
      static long gcd(long a, long b) {return b == 0 ? a : gcd(b, a % b);}
      static int[] exgcd(int a, int b) {if (b == 0) return new int[] {1, 0}; int[] y = exgcd(b, a % b); return new int[] {y[1], y[0] - y[1] * (a / b)};}
      static long[] exgcd(long a, long b) {if (b == 0) return new long[] {1, 0}; long[] y = exgcd(b, a % b); return new long[] {y[1], y[0] - y[1] * (a / b)};}
      static int randInt(int min, int max) {return __r.nextInt(max - min + 1) + min;}
      static long mix(long x) {x += 0x9e3779b97f4a7c15L; x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9L; x = (x ^ (x >> 27)) * 0x94d049bb133111ebL; return x ^ (x >> 31);}
      // array util
      static void reverse(int[] a) {for (int i = 0, n = a.length, half = n / 2; i < half; ++i) {int swap = a[i]; a[i] = a[n - i - 1]; a[n - i - 1] = swap;}}
      static void reverse(long[] a) {for (int i = 0, n = a.length, half = n / 2; i < half; ++i) {long swap = a[i]; a[i] = a[n - i - 1]; a[n - i - 1] = swap;}}
      static void reverse(double[] a) {for (int i = 0, n = a.length, half = n / 2; i < half; ++i) {double swap = a[i]; a[i] = a[n - i - 1]; a[n - i - 1] = swap;}}
      static void reverse(char[] a) {for (int i = 0, n = a.length, half = n / 2; i < half; ++i) {char swap = a[i]; a[i] = a[n - i - 1]; a[n - i - 1] = swap;}}
      static void shuffle(int[] a) {int n = a.length - 1; for (int i = 0; i < n; ++i) {int ind = randInt(i, n); int swap = a[i]; a[i] = a[ind]; a[ind] = swap;}}
      static void shuffle(long[] a) {int n = a.length - 1; for (int i = 0; i < n; ++i) {int ind = randInt(i, n); long swap = a[i]; a[i] = a[ind]; a[ind] = swap;}}
      static void shuffle(double[] a) {int n = a.length - 1; for (int i = 0; i < n; ++i) {int ind = randInt(i, n); double swap = a[i]; a[i] = a[ind]; a[ind] = swap;}}
      static void rsort(int[] a) {shuffle(a); sort(a);}
      static void rsort(long[] a) {shuffle(a); sort(a);}
      static void rsort(double[] a) {shuffle(a); sort(a);}
      static int[] copy(int[] a) {int[] ans = new int[a.length]; for (int i = 0; i < a.length; ++i) ans[i] = a[i]; return ans;}
      static long[] copy(long[] a) {long[] ans = new long[a.length]; for (int i = 0; i < a.length; ++i) ans[i] = a[i]; return ans;}
      static double[] copy(double[] a) {double[] ans = new double[a.length]; for (int i = 0; i < a.length; ++i) ans[i] = a[i]; return ans;}
      static char[] copy(char[] a) {char[] ans = new char[a.length]; for (int i = 0; i < a.length; ++i) ans[i] = a[i]; return ans;}
      // input
      static void r() throws IOException {input = new StringTokenizer(rline());}
      static int ri() throws IOException {return Integer.parseInt(rline());}
      static long rl() throws IOException {return Long.parseLong(rline());}
      static double rd() throws IOException {return Double.parseDouble(rline());}
      static int[] ria(int n) throws IOException {int[] a = new int[n]; r(); for (int i = 0; i < n; ++i) a[i] = ni(); return a;}
      static void ria(int[] a) throws IOException {int n = a.length; r(); for (int i = 0; i < n; ++i) a[i] = ni();}
      static int[] riam1(int n) throws IOException {int[] a = new int[n]; r(); for (int i = 0; i < n; ++i) a[i] = ni() - 1; return a;}
      static void riam1(int[] a) throws IOException {int n = a.length; r(); for (int i = 0; i < n; ++i) a[i] = ni() - 1;}
      static long[] rla(int n) throws IOException {long[] a = new long[n]; r(); for (int i = 0; i < n; ++i) a[i] = nl(); return a;}
      static void rla(long[] a) throws IOException {int n = a.length; r(); for (int i = 0; i < n; ++i) a[i] = nl();}
      static double[] rda(int n) throws IOException {double[] a = new double[n]; r(); for (int i = 0; i < n; ++i) a[i] = nd(); return a;}
      static void rda(double[] a) throws IOException {int n = a.length; r(); for (int i = 0; i < n; ++i) a[i] = nd();}
      static char[] rcha() throws IOException {return rline().toCharArray();}
      static void rcha(char[] a) throws IOException {int n = a.length, i = 0; for (char c : rline().toCharArray()) a[i++] = c;}
      static String rline() throws IOException {return __i.readLine();}
      static String n() {return input.nextToken();}
      static int rni() throws IOException {r(); return ni();}
      static int ni() {return Integer.parseInt(n());}
      static long rnl() throws IOException {r(); return nl();}
      static long nl() {return Long.parseLong(n());}
      static double rnd() throws IOException {r(); return nd();}
      static double nd() {return Double.parseDouble(n());}
      // output
      static void pr(int i) {__o.print(i);}
      static void prln(int i) {__o.println(i);}
      static void pr(long l) {__o.print(l);}
      static void prln(long l) {__o.println(l);}
      static void pr(double d) {__o.print(d);}
      static void prln(double d) {__o.println(d);}
      static void pr(char c) {__o.print(c);}
      static void prln(char c) {__o.println(c);}
      static void pr(char[] s) {__o.print(new String(s));}
      static void prln(char[] s) {__o.println(new String(s));}
      static void pr(String s) {__o.print(s);}
      static void prln(String s) {__o.println(s);}
      static void pr(Object o) {__o.print(o);}
      static void prln(Object o) {__o.println(o);}
      static void prln() {__o.println();}
      static void pryes() {prln("yes");}
      static void pry() {prln("Yes");}
      static void prY() {prln("YES");}
      static void prno() {prln("no");}
      static void prn() {prln("No");}
      static void prN() {prln("NO");}
      static boolean pryesno(boolean b) {prln(b ? "yes" : "no"); return b;};
      static boolean pryn(boolean b) {prln(b ? "Yes" : "No"); return b;}
      static boolean prYN(boolean b) {prln(b ? "YES" : "NO"); return b;}
      static void prln(int... a) {for (int i = 0, len = a.length - 1; i < len; pr(a[i]), pr(' '), ++i); if (a.length > 0) prln(a[a.length - 1]); else prln();}
      static void prln(long... a) {for (int i = 0, len = a.length - 1; i < len; pr(a[i]), pr(' '), ++i); if (a.length > 0) prln(a[a.length - 1]); else prln();}
      static void prln(double... a) {for (int i = 0, len = a.length - 1; i < len; pr(a[i]), pr(' '), ++i); if (a.length > 0) prln(a[a.length - 1]); else prln();}
      static <T> void prln(Collection<T> c) {int n = c.size() - 1; Iterator<T> iter = c.iterator(); for (int i = 0; i < n; pr(iter.next()), pr(' '), ++i); if (n >= 0) prln(iter.next()); else prln();}
      static void h() {prln("hlfd"); flush();}
      static void flush() {__o.flush();}
      static void close() {__o.close();}
  }