1869880_ac_0ms_20k.c

北大大牛代码 1240道题的原代码 超级权威

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

int main()
{
  int k, i, n;
  int plaincode[80], ciphercode[80];
  char plaintext[80], ciphertext[80];

  while(scanf("%d",&k)==1&&k)
  {
   memset(ciphertext,'0',sizeof(ciphertext));
   scanf("%s",ciphertext);
   n = strlen(ciphertext);
   memset(plaintext,'0',n);
   for(i = 0; i < n; i++)
   {
    switch(ciphertext[i])
    {
     case '_': ciphercode[i] = 0;break;
     case '.': ciphercode[i] = 27;break;
     default : ciphercode[i] = (int)ciphertext[i]-96;
    }
    plaincode[(k*i)%n]=(ciphercode[i]+i)%28;
    if(plaincode[(k*i)%n]<0) plaincode[(k*i)%n]+=28;
    switch(plaincode[(k*i)%n])
    {
     case 0: plaintext[(k*i)%n] = '_';break;
     case 27: plaintext[(k*i)%n] = '.';break;
     default : plaintext[(k*i)%n] = (char)(plaincode[(k*i)%n]+96);
    }
  }
  plaintext[n] = '\0';
  puts(plaintext);
 }
}