667. Beautiful Arrangement II 美丽的安排2

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

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

If there are multiple answers, print 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.

Note:

1. The n and k are in the range 1 <= k < n <= 10⁴.

/**
 * @param {number} n
 * @param {number} k
 * @return {number[]}
 */
var constructArray = function (n, k) {
    let res = [];
    for (let i = 1, j = n; i <= j;) {
        if (k > 1) {
            res.push(k-- % 2 ? i++ : j--);
        } else {
            res.push(i++);
        }
    }
    return res;
};
let n = 3;
let k = 2;
let res = constructArray(n, k);
console.log(res);

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