LC 667. Beautiful Arrangement II

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 kdistinct 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:

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

Runtime: 28 ms, faster than 39.80% of C++ online submissions for Beautiful Arrangement II.

构造题

最小，k=1是顺序或者倒序的排列。

最大，k=n-1是依此从两头挑数的排列。

根据k来判断要排多少个头尾数。

#include <vector>

#include <iostream>

using namespace std;

class Solution {

public:

  vector<int> constructArray(int n, int k) {

    int tmp = k/;

    vector<int> ret;

    int idx = ;

    while(tmp){

      ret.push_back(idx);

      ret.push_back(n+ - idx);

      idx++;

      tmp--;

    }

    if(k %  == ){

      for(int i = idx; i<= n+-idx; i++) ret.push_back(i);

    }else for(int i=n+-idx; i>=idx; i--) ret.push_back(i);

    return ret;

  }

};

巴特西

LC 667. Beautiful Arrangement II

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