hdu-1129（模拟题）

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=1129

注意：c_code[i]=(p_code[i*k%n]-i)%28;

#include<iostream>
#include<cstring>
#include<cstdio>
#include<map>
using namespace std;
char dc[50]={'_','a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t',
'u','v','w','x','y','z','.'};
map <char,int> mp;
char str[120];
int pcode[120],ccode[120];
int main(void)
{
    mp['_']=0;mp['a']=1;mp['b']=2;mp['c']=3;mp['d']=4;mp['e']=5;mp['f']=6;mp['g']=7;mp['h']=8;mp['i']=9;
    mp['j']=10;mp['k']=11;mp['l']=12;mp['m']=13;mp['n']=14;mp['o']=15;mp['p']=16;mp['q']=17;mp['r']=18;
    mp['s']=19;mp['t']=20;mp['u']=21;mp['v']=22;mp['w']=23;mp['x']=24;mp['y']=25;mp['z']=26;mp['.']=27;
    int n,len,i,j,k;
    while(~scanf("%d",&k)&&k)
    {
        scanf("%s",str);
        len=strlen(str);
        for(i=0;i<len;i++)
        {
            ccode[i]=mp[str[i]];
            pcode[i*k%len]=(ccode[i]+i)%28;
        }
        for(i=0;i<len;i++) printf("%c",dc[pcode[i]]);
        printf("\n");
    }
    return 0;
}