Убрать повторяющиеся слова при создании словаря из текста

#include <stdio.h>
#include <conio.h>
#include <string.h>
int main(void)
{
    char str[255 + 1];
    char data3[] = "D://data3.txt";
    char data33[] = "D://data33.txt";
    FILE* fid, * fid2;
    errno_t err;
    if ((fopen_s(&fid, "D://data3.txt", "r")) || (err = fopen_s(&fid2, "D://data33.txt", "w")) != 0)
    {
        printf("\n\t The file could not be opened.\n");
        printf("\nPress and key: ");
        _getch();
        return -1;
    }
    char ch;
    fprintf(fid2, "\nСловарь\n\n");
    while ((ch = getc(fid)) != EOF)
    {
        if (ch == ' ')
        {
            ch--;
            fprintf(fid2, "\n");
        }
        fputc(ch, fid2);
    }
    fclose(fid);
    fclose(fid2);
    printf("Read the iformation was produced from a file %s\n", data3);
    printf("Recorded iformation has been made to the file %s\n", data33);
    printf("\nPress and key: ");
    _getch();
    return 0;
}

#define  DELIM ".,; ?!"
 
int main()
{
    const char *str = "one? three four one five, two one seven! nine two; eight three five two three, six.";
    char *copystr = _strdup( str ), *p;
 
    printf( "string:\n\t%s\n\n", str );
    strcpy( copystr, str );
    printf( "result:\n" );
 
    for( p = strtok( copystr, DELIM ); p; p = strtok( NULL, DELIM ) )
        if( strstr( str, p ) - str == p - copystr )
            printf( "\t%s\n", p );
 
    free( copystr );
    return 0;
}