Codeforces GYM 100114 C. Sequence 打表

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C. Sequence

Time Limit: 1 Sec  

Memory Limit: 256 MB

題目串連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.

InputThe first line contains an integer n, the number of sequence member to be calculated.OutputThe output file should contain a single integer k, the value of the n-th member of the sequenceSample Input

1

Sample Output1HINT1 ≤ n ≤ 2 147 483 647.

題意

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

規律是上一個，是前一個數乘以2之後，數字按字典序排列之後的樣子

題解：

打表之後，發現後面都是6個一個迴圈的，直接輸出就好了

代碼：

#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;}

 

Codeforces GYM 100114 C. Sequence 打表