供参考:
#include<stdio.h>
int main()
{
char s[1024],*p,*q;
gets(s);
p = q = s;
while(*p){
if((*p >= 'A' && *p <= 'Z')||(*p >='a' && *p <= 'z')){
*q++ = *p++;
}else p++;
}
*q = '\0';
puts(s);
return 0;
}