版本1：使用 getchar_unlocked 作为R塞缪尔Klatchko（见注释）建议

Version 1 : Using getchar_unlocked as suggested by R Samuel Klatchko (see comments)

#define BUFSIZE 32*1024
int main(){
  int lines, number=0, dividend, ans=0;
  char c;
  setvbuf(stdin, (char*)NULL, _IOFBF, 0);// full buffering mode
  scanf("%d%d\n", &lines, &dividend);
  while(lines>0){
    c = getchar_unlocked();
    //parse the number using characters
    //each number is on a separate line
    if(c=='\n'){
      if(number % dividend == 0)    ans += 1;
      lines -= 1;
      number = 0;
    }
    else
      number = c - '0' + 10*number;
  }

  printf("%d are divisible by %d \n", ans, dividend);
  return 0;
}

版本2：使用 FREAD 来读取它的块和解析数

#define BUFSIZE 32*1024
int main(){
int lines, number=0, dividend, ans=0, i, chars_read;
char buf[BUFSIZE+1] = {0}; //initialise all elements to 0
scanf("%d%d\n",&lines, &dividend);

while((chars_read = fread(buf, 1, BUFSIZE, stdin)) > 0){
  //read the chars from buf
  for(i=0; i < chars_read; i++){
    //parse the number using characters
    //each number is on a separate line
    if(buf[i] != '\n')
      number = buf[i] - '0' + 10*number;
    else{
      if(number%dividend==0)    ans += 1;
      lines -= 1;
      number = 0;
    }       
  }

if(lines==0)  break;
}

printf("%d are divisible by %d \n", ans, dividend);
return 0;
}

结果：（10万个号码由11整除测试）

Results: (10 million numbers tested for divisibility by 11)

运行1：（不setvbuf用来第1版）0.782秒结果
  运行2：（与setvbuf用来版本1）0.684秒结果
  运行3：（第2版）0.534

Run 1: ( Version 1 without setvbuf ) 0.782 secs
Run 2: ( Version 1 with setvbuf ) 0.684 secs
Run 3: ( Version 2 ) 0.534

P.S。 - 每次运行使用-O1标志GCC编译

P.S. - Every run compiled with GCC using -O1 flag