LeetCode in Kotlin

667. Beautiful Arrangement II

Medium

Given two integers n and k, construct a list answer that contains n different positive integers ranging from 1 to n and obeys the following requirement:

• Suppose this list is answer = [a1, a2, a3, ... , an], then the list [|a1 - a2|, |a2 - a3|, |a3 - a4|, ... , |an-1 - an|] has exactly k distinct integers.

Return the list answer. If there multiple valid answers, return any of them.

Example 1:

Input: n = 3, k = 1

Output: [1,2,3] Explanation: The [1,2,3] has three different positive integers ranging from 1 to 3, and the [1,1] has exactly 1 distinct integer: 1

Example 2:

Input: n = 3, k = 2

Output: [1,3,2] Explanation: The [1,3,2] has three different positive integers ranging from 1 to 3, and the [2,1] has exactly 2 distinct integers: 1 and 2.

Constraints:

• 1 <= k < n <= 104

Solution

@Suppress("NAME_SHADOWING")
class Solution {
    fun constructArray(n: Int, k: Int): IntArray {
        var k = k
        val res = IntArray(n)
        var left = 1
        var right = n
        for (i in 0 until n) {
            res[i] = if (k % 2 == 0) left++ else right--
            if (k > 1) {
                k--
            }
        }
        return res
    }
}

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