poj1026 문제 풀이 보고서

Cipher
Time Limit: 1000MS
 
Memory Limit: 10000K
Total Submissions: 13633
 
Accepted: 3438
Description
Bob and Alice started to use a brand-new encoding scheme. Surprisingly it is not a Public Key Cryptosystem, but their encoding and decoding is based on secret keys. They chose the secret key at their last meeting in Philadelphia on February 16th, 1996. They chose as a secret key a sequence of n distinct integers, a1 ; . . .; an, greater than zero and less or equal to n. The encoding is based on the following principle. The message is written down below the key, so that characters in the message and numbers in the key are correspondingly aligned. Character in the message at the position i is written in the encoded message at the position ai, where ai is the corresponding number in the key. And then the encoded message is encoded in the same way. This process is repeated k times. After kth encoding they exchange their message. 
The length of the message is always less or equal than n. If the message is shorter than n, then spaces are added to the end of the message to get the message with the length n. 
Help Alice and Bob and write program which reads the key and then a sequence of pairs consisting of k and message to be encoded k times and produces a list of encoded messages. 
Input
The input file consists of several blocks. Each block has a number 0 < n <= 200 in the first line. The next line contains a sequence of n numbers pairwise distinct and each greater than zero and less or equal than n. Next lines contain integer number k and one message of ascii characters separated by one space. The lines are ended with eol, this eol does not belong to the message. The block ends with the separate line with the number 0. After the last block there is in separate line the number 0.
Output
Output is divided into blocks corresponding to the input blocks. Each block contains the encoded input messages in the same order as in input file. Each encoded message in the output file has the lenght n. After each block there is one empty line.
Sample Input

10
4 5 3 7 2 8 1 6 10 9
1 Hello Bob
1995 CERC
0
0

Sample Output

BolHeol  b
C RCE

한 번 살펴보니 이것은 바로 고찰과 교환 문제이다. 난이도가 별로 없을 것 같다. 그리고 생각도 하지 않고 바로 모의 방식으로 썼다. 제출해서 TLE를 발견했다. 처음 배운 것은 경험이 없고 이 방면의 문제를 처음 풀었기 때문에 반나절을 생각해도 좋은 방법이 없었다. 그래서 인터넷에서 소들의 문제 풀이 보고서를 찾아서 이 문제가 줄 수 있는 데이터가 매우 크다는 것을 알게 되었다.먼저 모든 위치를 바꾸는 주기를 구해서 t[i]로 기억하고 변환할 때 각 위치의 변환(k%t[i])을 한 번 한 다음에 Ok를 해야 한다.다음은 제가 쓴 코드입니다. 큰 소들의 코드와 비교하면 큰 차이가 있습니다. 허허, 계속 노력할 수밖에 없습니다!
코드:
언어: c++
#include #include #include using namespace std; int main() { int k,n,t[210],change[210],tt; char a1[210],a2[210]; while(cin>>n) { if(n==0) break; for(int i=0;i>change[i]; memset(t,0,sizeof(t)); for(int i=0;i>k) { if(k==0) break; getchar(); cin.getline(a1,n+1); int len=strlen(a1); for(int i=len;i