/*
Print the letters contained in a sentence, in alphabetical order.
Example, input of "helloworld." produces "D  E  H  L  O  R  W "
*/

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

typedef enum { false, true} Boolean;

int main(void)
{
    int found[256] = { false }; /* indicate no letters found */

    char letter;
    char index;

    printf ("Enter a sentence terminated by a period.\n");
    scanf("%c", &letter);

    /* Read and mark letters found */
    while (letter != '.')
    {
        letter = toupper(letter);
        found[(int)letter] = true;
        scanf("%c", &letter);
    }

    /* Display the found letters in order */
    for (index = 'A'; index <= 'Z'; index++)
    {
        if (found[(int)index]) 
        {
            printf(" %c ", index);
        }
    }
    printf("\n\n");

    return 0;
}