Codeforces Round 954 (Div. 3) |
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You are given an array of integers a1,a2,…,an and an integer k. You need to make it beautiful with the least amount of operations.
Before applying operations, you can shuffle the array elements as you like. For one operation, you can do the following:
The array b1,b2,…,bn is beautiful if bi=bn−i+1 for all 1≤i≤n.
Find the minimum number of operations needed to make the array beautiful, or report that it is impossible.
Each test consists of several sets of input data. The first line contains a single integer t (1≤t≤104) — the number of sets of input data. Then follows their description.
The first line of each set of input data contains two integers n and k (1≤n≤105, 1≤k≤109) — the size of the array a and the number k from the problem statement.
The second line of each set of input data contains n integers a1,a2,…,an (1≤ai≤109) — the elements of the array a.
It is guaranteed that the sum of n over all sets of input data does not exceed 2⋅105.
For each set of input data, output the minimum number of operations needed to make the array beautiful, or −1 if it is impossible.
111 100000000012 1624323799 7082903233 13 2 14 17 1 5 35 111 2 15 7 107 11 8 2 16 8 16 3113 12 1 1 3 3 11 12 22 45 777 777 1500 7410 21 2 1 2 1 2 1 2 1 211 21 2 1 2 1 2 1 2 1 2 113 32 3 9 14 17 10 22 20 18 30 1 4 285 12 3 5 3 5
0 83966524 1 4 6 1 48 -1 0 14 0
In the first set of input data, the array is already beautiful.
In the second set of input data, you can shuffle the array before the operations and perform the operation with index i=1 for 83966524 times.
In the third set of input data, you can shuffle the array a and make it equal to [2,3,1]. Then apply the operation with index i=3 to get the array [2,3,2], which is beautiful.
In the eighth set of input data, there is no set of operations and no way to shuffle the elements to make the array beautiful.
In the ninth set of input data, the array is already beautiful.
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