https://codeforces.com/gym/105386/problem/G

题目： 

结论：

从0开始每四个相邻数的异或值为0

代码：

#include<bits/stdc++.h>
using namespace std;
#define int long long
void solve() {
    int n;
    cin >> n;
    if(n==1||n%4==0)
    {
		cout << "impossible" << endl;
	}
	else{
		int cnt=2;
		cout << 1 << ' ' << 0 << ' ';
		for(int i=2;i<n;)
		{
			cnt++;
			if(cnt%4==0)
			{
				cout << i+1 <<' '<< i << ' ';
				i+=2;cnt++;
			}
			else {
			cout << i << ' ' ;i++; 
		}
	}
	cout << endl;
	}
	
}
signed main() {
    int t;cin>>t;
    while(t--)solve();
}