hdu2062 Subset sequence

Problem Description

Consider the aggregate An= { 1, 2, …, n }. For example, A1={1}, A3={1,2,3}. A subset sequence is defined as a array of a non-empty subset. Sort all the subset sequece of An in lexicography order. Your task is to find the m-th one.

 

Input

The input contains several test cases. Each test case consists of two numbers n and m ( 0< n<= 20, 0< m<= the total number of the subset sequence of An ).

 

Output

For each test case, you should output the m-th subset sequence of An in one line.

 

Sample Input

1 1
2 1
2 2
2 3
2 4
3 10

 

Sample Output

1
1
1 2
2
2 1
2 3 1

 

题解：

http://blog.youkuaiyun.com/lianqi15571/article/details/8877014

看他的递推关系。

vector的练习。erase，clear，不能memset，如何加元素。

cout << '\b' << '\n' ;   是过不了编译的。

下面是代码：

#include<iostream>
#include<vector>
#include<cstring>
using namespace std;
int main()
{
	long long m,n;
	long long f[25];
	memset(f,0,sizeof(f));
	f[1] = 1;
	for(int i=2;i<25;i++){
		f[i] = i*(f[i-1]+1);
	}
	vector<int> coor; 
	while(cin >> n >> m){

		for(int i=0;i<n;i++)
			coor.push_back(i+1); 
		int cnt = n;
		while(m!=0){
			long long temp = f[cnt]/cnt;
			long long pos = (m-1)/temp;
			cout << coor[pos] ;
			coor.erase(coor.begin()+pos);
			cnt--;
			m =  m - pos*temp -1;    //减一要注意。
			if(m==0)
				cout << '\n';
			else cout << ' ';
		}	
		coor.clear();
	} 
 }