#3470

Permutations IV

hard · 34% accepted · 28 likes · top 11%

array · math · combinatorics · enumeration

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Description

Given two integers, n and k, an alternating permutation is a permutation of the first n positive integers such that no two adjacent elements are both odd or both even.

Return the k-th alternating permutation sorted in lexicographical order. If there are fewer than k valid alternating permutations, return an empty list.

Solution