Leetcode•Mar 04, 2026

Beautiful Arrangement II

Hazrat Ali

Leetcode

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.

Solution
var constructArray = function(n, k) {
    let result = [];
   
    let left = 1;
    let right = k + 1;
   
    while (left <= right) {
        result.push(left++);
        if (left <= right) {
            result.push(right--);
        }
    }
   
    for (let i = k + 2; i <= n; i++) {
        result.push(i);
    }
   
    return result;
};



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