The 15th UESTC Programming Contest Preliminary J - Jermutat1on cdoj1567

地址：http://acm.uestc.edu.cn/#/problem/show/1567

题目：

Jermutat1on

Time Limit: 3000/1000MS (Java/Others)     Memory Limit: 65535/65535KB (Java/Others)

Submit Status

You are given two numbers nn and kk.

You are required to construct a permutation p1,p2,...,pnp1,p2,...,pn of numbers 1,2,...,n1,2,...,n such that there are exactly kk different numbers in |p1−p2||p1−p2|, |p2−p3||p2−p3|, ..., |pn−1−pn||pn−1−pn|.

Input

Only one line contains two integers nn and kk.

1≤k<n≤1000001≤k<n≤100000.

Output

Print nn integers forming the permutation.

If there are multiple answers, print any of them.

If there are no such permutation, print -1.

Sample input and output

Sample Input	Sample Output
3 1	1 2 3

Source

The 15th UESTC Programming Contest Preliminary

 思路：水题，见代码。

 #include<iostream>
 using namespace std;

 int n,k;

 int gcd(int x,int y)
 {
     if(y==)
         return x;
     else
         return gcd(y,x%y);
 }

 int main()
 {
     cin>>n>>k;
     if(k>=n)
         cout<<-<<endl;
     else
     {
         if(k==)
             for(int i=;i<=n;i++)
                 cout<<i<<' ';
         else if(k%)
         {
             int mid=(k+)/;
             cout<<mid<<' ';
             for(int i=;i<=k;i++)
             {
                 if(i%)
                     cout<<(mid+=i)<<' ';
                 else
                     cout<<(mid-=i)<<' ';
             }
             for(int i=mid+;i<=n;i++)
                 cout<<i<<' ';
         }
         else
         {
             int mid=k/+;
             cout<<mid<<' ';
             for(int i=;i<=k;i++)
             {
                 if(i%)
                     cout<<(mid-=i)<<' ';
                 else
                     cout<<(mid+=i)<<' ';
             }
             for(int i=mid+;i<=n;i++)
                 cout<<i<<' ';
         }
     }
     return ;
 }