It is obvious that some beams emitted by distinct lasers can intersect. If two beams intersect each other, one joule of energy is released per second because of the interaction of the beams. So the more beams intersect, the more energy is released. Innokentiy noticed that if the energy generator releases exactly k joules per second, the perpetuum mobile will work up to 10 times longer. The scientist can direct any laser at any receiver, but he hasn‘t thought of such a construction that will give exactly the required amount of energy yet. You should help the scientist to tune up the generator.
The only line contains two integers n and k (1 ≤ n ≤ 200000, 
) separated by space — the number of lasers in the energy generator and the power of the generator Innokentiy wants to reach.
Output n integers separated by spaces. i-th number should be equal to the number of receiver which the i-th laser should be directed at. Both lasers and receivers are numbered from 1 to n. It is guaranteed that the solution exists. If there are several solutions, you can output any of them.
4 5
4 2 3 1
5 7
4 2 5 3 1
6 0
1 2 3 4 5 6
其实就是 求n的序列 的逆序对数为k；代码比较简单只是难以想到
#include<iostream> using namespace std; int main(){ int n;long long int k; while(cin>>n>>k){ int flag=n,t=1; for(int i=1;i<=n;i++){ if(k>=n-i){ k-=n-i; cout<<flag--<<" "; }else{ cout<<t++<<" "; } } cout<<endl; } return 0; }
原文：http://www.cnblogs.com/demodemo/p/4716150.html
