Cipher
| Time Limit: 1000MS | Memory Limit: 10000K | |
| Total Submissions: 18970 | Accepted: 5067 |
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
求置换的循环节
1 #include <stdio.h>
2 #include <stdlib.h>
3 #include <string.h>
4 #define MAX 202
5 int key[MAX], t[MAX];
6 void get_time(int n)
7 {
8 int i, j, count;
9 for (i = 1; i <= n; i++)
10 {
11 j = key[i];
12 count = 1;
13 while(i != j)
14 {
15 count++;
16 j = key[j];
17 }
18 t[i] = count;
19 }
20 }
21 int main()
22 {
23 int i, j, k, n, len;
24 char src[MAX], dst[MAX];
25
26 while(scanf("%d", &n)&&n)
27 {
28 for (i = 1; i <= n; i++)
29 scanf("%d", &key[i]);
30 memset(t, 0, sizeof(t));
31 get_time(n);
32 while(scanf("%d", &k)&&k)
33 {
34 getchar();
35 gets(src + 1);
36 for (i = strlen(src + 1) + 1; i <= n; i++)
37 src[i] = ‘ ‘;
38 src[n + 1] = 0;
39 for (i = 1; i <= n; i++)
40 {
41 int pos = i;
42 for (j = 0; j < k % t[i]; j++)
43 pos = key[pos];
44 dst[pos] = src[i];
45 }
46 dst[n + 1] = 0;
47 puts(dst + 1);
48 }
49 printf("\n");
50 }
51 return 0;
52 }