enum（枚举类型）

 1 #include<stdio.h>
 2 
 3 int main(void)
 4 {
 5  enum state {in,out};        //in the space state
 6 
 7  char c;
 8  enum state s;
 9 
10  s = out;
11  while ((c = getchar()) != EOF)
12  {
13   if (c == ‘ ‘)
14    s = in;
15   else
16   {
17    if (s == in)
18    {
19     putchar(‘ ‘);
20     s = out;
21    } 
22    putchar(c);
23   }
24  }
25  return 0;
26 }