667. Beautiful Arrangement II

Posted 2020-10-05 无惧风云

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, ... , an], then the list [|a1 - a2|, |a2 - a3|, |a3 - a4|, ... , |an-1 - an|] 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.

 

 

 

 1 class Solution {
 2 public:
 3     vector<int> constructArray(int n, int k) {
 4       vector<int> vet(n);
 5         for (int i = 0;i < n;i++)
 6         {
 7             vet[i] = i + 1;
 8         }
 9         vector<int> vet1;
10         vector<int> vet2;
11         for (int i = n - k - 1;i<n ;i++)
12         {
13             vet1.push_back(vet[i]);
14         }
15         int len = vet1.size();
16         int m = 0,m1 = len - 1;
17         //cout << m << m1 << endl;
18         bool flag = true;
19         while (m <= m1)
20         {
21             
22             if (flag == true)
23             {
24                 vet2.push_back(vet1[m1]);
25         
26                 m1--;
27                 flag = false;
28             }
29             else
30             {
31                 vet2.push_back(vet1[m]);
32                 m++;
33                 flag = true;
34             }
35         }
36     
37         for (int i = n - 1 - k-1;i >=0 ;i--)
38         {
39             vet2.push_back(vet[i]);
40         }
41         return vet2;
42     }
43 };