练习 6-4 编写一个程序，根据单词的出现频率按降序打印输入的各个不同单词，并在 每个单词的前面标上它的出现次数

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

#define MAXWORD 100

/*Author Stat:  founded 2017 11 26*/
static size_t word_count = 0;

struct line{
   char *word;
   size_t count;
   struct line *next;
};


int getword(char *,int);
struct line *additem(struct line *,char *);
void swapcontent(struct line *,struct line *);
void showitem(struct line *);
struct line *talloc(void);
char *strdup(char *);


int main(void)
{
   struct line *head;
   char word[MAXWORD];


   head = NULL;
   while(getword(word,MAXWORD) != EOF)
      if(isalpha(word[0]))
         head = additem(head,word);
   printf("Total word: %lu\n",word_coun