Codeforces GYM 100114 C. Sequence 打表

C. Sequence

Time Limit: 1 Sec  

Memory Limit: 256 MB

题目连接

http://codeforces.com/gym/100114

Description

Integer sequences are very interesting mathematical objects. Let us examine a sequence generated with the use of two operations: doubling and “digit sorting”. The latter operation consists in ascending-order sort of the individual digits in the decimal representation of the argument. For example, “digit sorting” of number 5726 gives 2567. The first member of the considered sequence is 1. To generate a member of the sequence from the previous member, double the previous one and apply “digit sorting” to the result. The first 15 members of the sequence are as follows: 1, 2, 4, 8, 16, 23, 46, 29, 58, 116, 223, 446, 289, 578, 1156, … Write a program to determine the value of the n-th member of this sequence.

Input

The first line contains an integer n, the number of sequence member to be calculated.

Output

The output file should contain a single integer k, the value of the n-th member of the sequence

Sample Input

1

Sample Output

1

HINT

1 ≤ n ≤ 2 147 483 647.

题意

1, 2, 4, 8, 16, 23, 46, 29, 58, 116, 223, 446, 289, 578, 1156

规律是上一个，是前一个数乘以2之后，数字按字典序排列之后的样子

题解：

打表之后，发现后面都是6个一个循环的，直接输出就好了

代码：

#include <iostream>
#include <cstdio>
#include <cmath>
#include <cstring>
#include <algorithm>

using namespace std;

int a[40]={0,1,2,4,8,16,23,46,29,58,116,223,446,289,578,1156,1223,2446,2489,4789,5789,11578,12356,12247,24449};
int b[10]={48889,77789,155578,111356,122227,244445};
int n;

int main()
{
    freopen("input.txt","r",stdin);
    freopen("output.txt","w",stdout);
    scanf("%d",&n);
    if(n<=24) printf("%d\n",a[n]);
        else printf("%d\n",b[(n-25)%6]);
    return 0;
}