Make array great again
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You are a citizen of Arrayland. Your President (Mr. P) has given you a mundane problem:
You're given an array a with size N (1-based indexing). You are allowed to perform an arbitrary number (including zero) of operations of the following type: choose an integer i (1 ≤ i ≤ N) and swap ai with aN-i+1.
Your goal is to make the array a great. An array is great if it satisfies one of the following conditions:
- a1 > a2 < a3 > a4 < ... aN
- a1 < a2 > a3 < a4 > ... aN
Compute the minimum number of operations necessary to make the array a great or determine that it's impossible to make it great.
- The first line of the input contains a single integer T denoting the number of test cases. The description of T test cases follows.
- The first line of each test case contains a single integer N denoting the size of the array a.
- The second line contains N space-separated integers a1, a2, ..., aN.
Print a single line containing one integer — the minimum number of operations required to make the array great, or -1 if it's impossible.
- 1 ≤ T ≤ 5
- 1 ≤ N ≤ 105
- 1 ≤ ai ≤ 109 for each valid i
Input: 1 6 1 2 3 4 5 6 Output: 1
Example case 1: The given array is NOT great. If you swap the second and the fifth element, then the array becomes great.
|Tags||cook90, dynamic-programming, medium, sidhant007|
|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, CLPS, PRLG, ICON, SCM qobi, PIKE, ST, NICE, LUA, BASH, LISP sbcl, LISP clisp, SCM guile, ERL, TCL, kotlin, TEXT, SCM chicken|
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