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 ;

 }

巴特西

The 15th UESTC Programming Contest Preliminary J - Jermutat1on cdoj1567