CF1716B.Permutation Chain

传统题 时间 2000 ms 内存 256 MiB 3 尝试 1 已通过 1 标签

Permutation Chain

A permutation of length nn is a sequence of integers from 11 to nn such that each integer appears in it exactly once.

Let the fixedness of a permutation pp be the number of fixed points in it — the number of positions jj such that pj=jp_j = j, where pjp_j is the jj-th element of the permutation pp.

You are asked to build a sequence of permutations a1,a2,a_1, a_2, \dots, starting from the identity permutation (permutation a1=[1,2,,n]a_1 = [1, 2, \dots, n]). Let's call it a permutation chain. Thus, aia_i is the ii-th permutation of length nn.

For every ii from 22 onwards, the permutation aia_i should be obtained from the permutation ai1a_{i-1} by swapping any two elements in it (not necessarily neighboring). The fixedness of the permutation aia_i should be strictly lower than the fixedness of the permutation ai1a_{i-1}.

Consider some chains for n=3n = 3:

  • a1=[1,2,3]a_1 = [1, 2, 3], a2=[1,3,2]a_2 = [1, 3, 2] — that is a valid chain of length 22. From a1a_1 to a2a_2, the elements on positions 22 and 33 get swapped, the fixedness decrease from 33 to 11.
  • a1=[2,1,3]a_1 = [2, 1, 3], a2=[3,1,2]a_2 = [3, 1, 2] — that is not a valid chain. The first permutation should always be [1,2,3][1, 2, 3] for n=3n = 3.
  • a1=[1,2,3]a_1 = [1, 2, 3], a2=[1,3,2]a_2 = [1, 3, 2], a3=[1,2,3]a_3 = [1, 2, 3] — that is not a valid chain. From a2a_2 to a3a_3, the elements on positions 22 and 33 get swapped but the fixedness increase from 11 to 33.
  • a1=[1,2,3]a_1 = [1, 2, 3], a2=[3,2,1]a_2 = [3, 2, 1], a3=[3,1,2]a_3 = [3, 1, 2] — that is a valid chain of length 33. From a1a_1 to a2a_2, the elements on positions 11 and 33 get swapped, the fixedness decrease from 33 to 11. From a2a_2 to a3a_3, the elements on positions 22 and 33 get swapped, the fixedness decrease from 11 to 00.

Find the longest permutation chain. If there are multiple longest answers, print any of them.

Input

The first line contains a single integer tt (1t991 \le t \le 99) — the number of testcases.

The only line of each testcase contains a single integer nn (2n1002 \le n \le 100) — the required length of permutations in the chain.

Output

For each testcase, first, print the length of a permutation chain kk.

Then print kk permutations a1,a2,,aka_1, a_2, \dots, a_k. a1a_1 should be an identity permutation of length nn ([1,2,,n][1, 2, \dots, n]). For each ii from 22 to kk, aia_i should be obtained by swapping two elements in ai1a_{i-1}. It should also have a strictly lower fixedness than ai1a_{i-1}.

Samples

2
2
3
2
1 2
2 1
3
1 2 3
3 2 1
3 1 2

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