Посчитать в строке количество слов, состоящих только из разных букв - C (СИ)

#include <stdio.h>
#include <string.h>
#include <conio.h>
#define MAX 1000
int diff_detect(char* p_str)
{
  char* pp;
  int i=0;
  const char* temp=p_str;
  for(pp=p_str;pp<(pp+strlen(p_str)-1);++pp)
  {
     i=strchr(temp,*pp)-strrchr(temp,*pp);
     if(i!=0)
     return 0;
  }
  return 1;
}
int diff_word(const char* str,const char* delim)
{
     char* buf, * p;
     int cnt=0;
  if ( ! str || ! delim )
    return -1;
  if ( ( buf = strdup(str) ) == NULL )
    return -1;
   for(p=strtok(buf,delim);p;p=strtok(NULL,delim))
   {
     if(diff_detect(p))
     ++cnt;
   }
   return cnt;
}
void main()
 {   char line[MAX];
     const char* w_border=" ";
     const char* p_line=line;
     printf("This application solves task 16 from laboratory work 4.\n");
     printf("*******************************************************************************\n");
     printf("Please input your string:\n");
     gets(line);
     printf("Number of words which consist of different letters is: %d\n",diff_word(p_line,w_border));
     getch();
 }