CSU1567 Reverse Rot

Reverse Rot

Description

A very simplistic scheme, which was used at one time to encode information, is to rotate the characters within an alphabet and rewrite them. ROT13 is the variant in which the characters A-Z are rotated 13 places, and it was a commonly used insecure scheme that attempted to "hide" data in many applications from the late 1990's and into the early 2000's.

It has been decided by Insecure Inc. to develop a product that "improves" upon this scheme by first reversing the entire string and then rotating it. As an example, if we apply this scheme to string ABCD with a reversal and rotation of 1, after the reversal we would have DCBA and then after rotating that by 1 position we have the result EDCB.

Your task is to implement this encoding scheme for strings that contain only capital letters, underscores, and periods. Rotations are to be performed using the alphabet order:

ABCDEFGHIJKLMNOPQRSTUVWXYZ_.
Note that underscore follows Z, and the period follows the underscore. Thus a forward rotation of 1 means 'A' is shifted to 'B', that is, 'A'→'B', 'B'→'C', ..., 'Z'→'_', '_'→'.', and '.'→'A'. Likewise a rotation of 3 means 'A'→'D', 'B'→'E', ..., '.'→'C'.

Input

Each input line will consist of an integer N, followed by a string. N is the amount of forward rotation, such that 1 ≤ N ≤ 27. The string is the message to be encrypted, and will consist of 1 to 40 characters, using only capital letters, underscores, and periods. The end of the input will be denoted by a final line with only the number 0.

Output

For each test case, display the "encrypted" message that results after being reversed and then shifted.

Sample Input

1 ABCD3 YO_THERE.1 .DOT14 ROAD9 SHIFTING_AND_ROTATING_IS_NOT_ENCRYPTING2 STRING_TO_BE_CONVERTED1 SNQZDRQDUDQ0

Sample Output

EDCBCHUHKWBR.UPEAROADPWRAYF_LWNHAXWH.RHPWRAJAX_HMWJHPWRAORQ.FGVTGXPQEAGDAQVAIPKTVUREVERSE_ROT

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题目的意思是给一个字符串，问把他倒置在每位加n得到的是什么

#include <iostream>#include <cstdio>#include <algorithm>#include <cmath>#include <cstring>#include <string>#include <queue>#include <stack>#include <set>#include <map>using namespace std;#define LL long longconst LL mod=1e9+7;const int INF=0x3f3f3f3f;#define MAXN 100005char s[100005];int n;char a[30]="ABCDEFGHIJKLMNOPQRSTUVWXYZ_.";int  b[100005];int main(){    while(~scanf("%d",&n)&&n)    {        scanf("%s",s);        int k=strlen(s);        for(int i=0; i<k/2; i++)        {            swap(s[i],s[k-i-1]);        }        for(int i=0; i<k; i++)        {            if(s[i]=='_')                b[i]=26;            else if(s[i]=='.')                b[i]=27;            else                b[i]=s[i]-'A';            b[i]+=n;            if(b[i]>27) b[i]-=28;        }        for(int i=0;i<k;i++)            printf("%c",a[b[i]]);        printf("\n");    }    return 0;}