A14216 | $Array and Peaks$

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题目描述

A sequence of $n$ integers is called a permutation if it contains all integers from $1$ to $n$ exactly once. Given two integers $n$ and $k$ , construct a permutation $a$ of numbers from $1$ to $n$ which has exactly $k$ peaks. An index $i$ of an array $a$ of size $n$ is said to be a peak if $1 < i < n$ and $a_i \gt a_{i-1}$ and $a_i \gt a_{i+1}$ . If such permutation is not possible, then print $-1$ .

The first line contains an integer $t$ ( $1 \leq t \leq 100$ ) — the number of test cases. Then $t$ lines follow, each containing two space-separated integers $n$ ( $1 \leq n \leq 100$ ) and $k$ ( $0 \leq k \leq n$ ) — the length of an array and the required number of peaks.

Output $t$ lines. For each test case, if there is no permutation with given length and number of peaks, then print $-1$ . Otherwise print a line containing $n$ space-separated integers which forms a permutation of numbers from $1$ to $n$ and contains exactly $k$ peaks. If there are multiple answers, print any.

输入 #1

输出 #1

1 
2 4 1 5 3 
-1
-1
1 3 6 5 4 2

C++ 编辑器

输入

输出