HDU 1027 Ignatius and the Princess II[DFS/全排列函数next_permutation]

Ignatius and the Princess II

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 9458    Accepted Submission(s): 5532

Problem Description

Now
our hero finds the door to the BEelzebub feng5166. He opens the door
and finds feng5166 is about to kill our pretty Princess. But now the
BEelzebub has to beat our hero first. feng5166 says, "I have three
question for you, if you can work them out, I will release the Princess,
or you will be my dinner, too." Ignatius says confidently, "OK, at
last, I will save the Princess."

"Now I will show you the first
problem." feng5166 says, "Given a sequence of number 1 to N, we define
that 1,2,3...N-1,N is the smallest sequence among all the sequence which
can be composed with number 1 to N(each number can be and should be use
only once in this problem). So it's easy to see the second smallest
sequence is 1,2,3...N,N-1. Now I will give you two numbers, N and M. You
should tell me the Mth smallest sequence which is composed with number 1
to N. It's easy, isn't is? Hahahahaha......"
Can you help Ignatius to solve this problem?

Input

The
input contains several test cases. Each test case consists of two
numbers, N and M(1<=N<=1000, 1<=M<=10000). You may assume
that there is always a sequence satisfied the BEelzebub's demand. The
input is terminated by the end of file.

Output

For
each test case, you only have to output the sequence satisfied the
BEelzebub's demand. When output a sequence, you should print a space
between two numbers, but do not output any spaces after the last number.

Sample Input

6 4
11 8

Sample Output

1 2 3 5 6 4
1 2 3 4 5 6 7 9 8 11 10

Author

Ignatius.L

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[题意]:1~n的全排列中的第m个排列

[分析]:使用next_permutation简便

[代码]:

#include <bits/stdc++.h>
using namespace std;
const int N=1e4+5;
#define INF 0x7fffffff
int n,m,a[N];
int main()
{
    while(cin>>n>>m){
    for(int i=1;i<=n;i++)
        a[i]=i; //初始化1~n的排列

     while(--m) //注意从1开始
        next_permutation(a+1,a+n+1); //1~n的排列的第m个

     for(int i=1;i<n;i++) //注意格式
            printf("%d ",a[i]);
        printf("%d\n",a[n]);
    }
}