LeetCode [932] Beautiful Array

 932. Beautiful Array

Medium

For some fixed N, an array A is beautiful if it is a permutation of the integers 1, 2, ..., N, such that:

For every i < j, there is no k with i < k < j such that A[k] * 2 = A[i] + A[j].

Given N, return any beautiful array A.  (It is guaranteed that one exists.)

 

Example 1:

Input: 4
Output: [2,1,4,3]

Example 2:

Input: 5
Output: [3,1,2,5,4]

 

Note:

• 1 <= N <= 1000

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class Solution { public int[] beautifulArray(int N) { List<Integer> list = new ArrayList<>(); list.add(1); while(list.size()<N){ List<Integer> tmp = new ArrayList<>(); for(int i : list){ if(i*2-1<=N) tmp.add(i*2-1); } for(int i : list){ if(i*2<=N) tmp.add(i*2); } list = tmp; } return list.stream().mapToInt(i->i).toArray(); } }