hdu 6235 Permutation

Permutation

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 262144/262144 K (Java/Others)
Total Submission(s): 179    Accepted Submission(s): 132
Special Judge

Problem Description

A permutation  p1,p2,...,pn of  1,2,...,n is called a lucky permutation if and only if  pi≡0(mod|pi−pi−2|) for  i=3...n.

Now you need to construct a lucky permutation with a given  n.

 

Input

The first line is the number of test cases.

For each test case, one single line contains a positive integer  n(3≤n≤105).

 

Output

For each test case, output a single line with  n numbers  p1,p2,...,pn.

It is guaranteed that there exists at least one solution. And if there are different solutions, print any one of them.

 

Sample Input

1 6

 

Sample Output

1 3 2 6 4 5

 

题意：构造满足pi%(|pi-pi-2|）==0的序列。

思路：i和i+2的奇偶性是相同的，所以奇偶序列是互不干扰的。根据pi%(|pi-pi-2|）==0推出，只要奇子序列的数和偶子序列的数分别是相邻的自然数就行了。

#include 
#include 
#include 
using namespace std;

int main()
{
    int t,n;
    scanf("%d",&t);
    while(t--)
    {
        scanf("%d",&n);
        int num1=1,num2=(n+1)/2+1,i=1;
        while(i<=n)
        {
            if(i%2==1)
            {
                if(i==1)
                    printf("%d",num1++),i++;
                else
                    printf(" %d",num1++),i++;
            }
            if(i%2==0&&i<=n)
                printf(" %d",num2++),i++;
        }
        printf("\n");
    }
    return 0;
}