/*------------------------------------------------------------------------------
 * binning.c: find first non-repeating letter in a string
**----------------------------------------------------------------------------*/

/* Copyright (c) 2009 Peter Bui. All Rights Reserved.
 *
 * Peter Bui <pbui@cse.nd.edu>
 *
**------------------------------------------------------------------------------
 * Includes
**----------------------------------------------------------------------------*/

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

/*------------------------------------------------------------------------------
 * Constants
**----------------------------------------------------------------------------*/

#define	MAX_STRLEN  128
#define NLETTERS    26

/*------------------------------------------------------------------------------
 * Functions
**----------------------------------------------------------------------------*/

char
find_first_nonrepeating_letter(char *s)
{
    char letter_count[NLETTERS];
    char *sptr;

    for(sptr = s; *sptr != 0; sptr++)
	if (isalpha(*sptr))
	    letter_count[tolower(*sptr) - 'a']++;

    for(sptr = s; *sptr != 0; sptr++)
	if (isalpha(*sptr))
	    if (letter_count[tolower(*sptr) - 'a'] == 1)
		return *sptr;

    return 0;
}

/*------------------------------------------------------------------------------
 * Main Execution
**----------------------------------------------------------------------------*/

int
main(int argc, char* argv[]) 
{
    char buffer[MAX_STRLEN];

    while (fgets(buffer, MAX_STRLEN, stdin)) 
	printf("%c\n", find_first_nonrepeating_letter(buffer));

    return (EXIT_SUCCESS);
}

/*------------------------------------------------------------------------------
 * vim: sts=4 sw=4 ts=8 ft=c
**----------------------------------------------------------------------------*/