Generating A Permutation
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For a permutation P = (p1, p2, ..., pN) of numbers [1, 2, ..., N], we define the function f(P) = max(p1, p2) + max(p2, p3) + ... + max(pN-1, pN).
You are given N and an integer K. Find and report a permutation P of [1, 2, ..., N] such that f(P) = K, if such a permutation exists.
Note f() = 0.
- The first line of the input contains an integer T denoting the number of test cases. The description of T test cases follows.
- The only line of each test case consists of two space-separated integers N, K respectively.
For each test case, if a permutation satisfying the condition exists, output a single line containing N space-separated integers which denotes any such permutation. If no such permutation exists, output a single integer -1 instead.
Use fast I/O methods since the size of the output is large.
- 1 ≤ T ≤ 40
- 1 ≤ N ≤ 105
- Sum of N over all test cases in each file ≤ 106
- 0 ≤ K ≤ 2 * 1010
Input: 3 4 12 2 2 5 14 Output: -1 1 2 5 4 3 2 1
Example 1. There doesn't exist any permutation of numbers [1, 2, 3, 4] that can have its f value equal to 4. Hence answer is -1.
Example 2. The permutations [1, 2] and [2, 1] both have their f values equal to 2. You can print any of these two permutations.
Example 3. The permutation [5, 4, 3, 2, 1] has f value = max(5, 4) + max(4, 3) + max(3, 2) + max(2, 1) = 5 + 4 + 3 + 2 = 14.
|Tags||acm17kgp, architk, constructive, easy-medium, kgp17rol|
|Time Limit:||1 sec|
|Source Limit:||50000 Bytes|
|Languages:||C, CPP14, JAVA, PYTH, PYTH 3.6, PYPY, CS2, PAS fpc, PAS gpc, RUBY, PHP, GO, NODEJS, HASK, rust, SCALA, swift, D, PERL, FORT, WSPC, ADA, CAML, ICK, BF, ASM, CLPS, PRLG, ICON, SCM qobi, PIKE, ST, NICE, LUA, BASH, NEM, LISP sbcl, LISP clisp, SCM guile, JS, ERL, TCL, kotlin, PERL6, TEXT, SCM chicken, CLOJ, COB, FS|
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