1006.cpp

zju_acm部分代码！都是自己做 有些事基本题目！题目还可以

#include <stdio.h>
#include <string.h>

int K,ciphercode[71],plaincode[71];
char ciphertext[71],plaintext[71];

int main()
{
	while(scanf("%d %s",&K,&ciphertext)!=EOF&&K)
	{
		int len=strlen(ciphertext);
		int i;
		for(i=0;i<len;i++)
		{
			if(ciphertext[i]!='.'&&ciphertext[i]!='_')
				ciphercode[i]=(int)ciphertext[i]-96;
			else
			{
				if(ciphertext[i]=='.')
					ciphercode[i]=27;
				else ciphercode[i]=0;
			}
		}
		for(i=0;i<len;i++)
		{
			plaincode[(K*i)%len]=(int)((-ciphercode[i]-i)/28)*28+ciphercode[i]+i;
			if(plaincode[(K*i)%len]!=0&&plaincode[(K*i)%len]!=27)
				plaintext[(K*i)%len] =char( (int)plaincode[(K*i)%len]+96);
			else {	if(plaincode[(K*i)%len]==0)
						plaintext[(K*i)%len]='_';
				
					else	plaintext[(K*i)%len]='.';
				}
		}
		
		printf("%s\n",plaintext);
		//for(i=0;i<len;i++)
		//{plaintext[i]='\0';}
		memset(plaintext,0,sizeof(plaintext));
		
	}
	return 0;
}