2012百度之星E题

#include"stdio.h"
#include"string.h"
#include"ctype.h"
int main()
{
 int i,j,fla1=1,fla2=1;
 char a[141];
 gets(a);
 int n=strlen(a);
 if(!islower(a[0]))
  {
   printf("Error!\n");
         return 0;
  }
    for(i=0;i<n;i++)
 {
  if(islower(a[i]))continue;
  if(a[i]=='_'&&i+1<n&&islower(a[i+1]))
  {fla1=0;i++;continue;}
  if(isupper(a[i]))
  {fla2=0;continue;}
        fla1=0;fla2=0;
  break;
 }
 if(fla1==0&&fla2==0)
  {
   printf("Error!\n");
  return 0;
  }
 if(fla1)
  for(i=0;i<n;i++)
  if(isupper(a[i]))
  {

   for(j=n+1;j>i+1;j--)
    a[j]=a[j-1];
   a[j]=tolower(a[i]);
   a[i]='_';
   n++;
  }
 if(fla2)
  for(i=0;i<n;i++)
  if(a[i]=='_'&&islower(a[i+1]))
  {
   n--;
   a[i]=toupper(a[i+1]);
   for(j=i+1;j<=n;j++)
    a[j]=a[j+1];
  }
    puts(a);

  return 0;
}