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Path: utzoo!watmath!clyde!burl!ulysses!allegra!mit-eddie!genrad!panda!talcott!harvard!seismo!rochester!bukys
From: bukys@rochester.UUCP (Liudvikas Bukys)
Newsgroups: net.sources
Subject: phone_gen -- a simple efficient general phone number letterizer
Message-ID: <14090@rochester.UUCP>
Date: Wed, 18-Dec-85 12:36:54 EST
Article-I.D.: rocheste.14090
Posted: Wed Dec 18 12:36:54 1985
Date-Received: Fri, 20-Dec-85 03:06:46 EST
References: <1206@panda.UUCP>
Distribution: net
Organization: U. of Rochester, CS Dept.
Lines: 48
Keywords: telephone number permutation

Here is a little program which does just what the recently-posted
"telno" program does, except that it is more general (no restrictions
on phone number format, no compiled-in array sizes), more efficient
(no big arrays, no calls to qsort()), and a lot simpler.

-------

/*
 * generate all alphabetic strings corresponding to a phone number
 *
 * n.b.: assumes I can modify argv[][] in place!
 */

int main(argc, argv)
int argc;
char **argv;
	{
	for (;  --argc > 0;  printf("\n"))
		phone_gen(*++argv, 0);

	return (0);
	}

char *table[] = { "abc", "def", "ghi", "jkl", "mno", "prs", "tuv", "wxy" };

phone_gen(s, i)
char *s;
int i;
	{
	char c, *s2;
	
	c = s[i];

	if (c == '\0')
		printf("%s\n", s);
	else if ('2' <= c && c <= '9')
		for (s2= table[c-'2'];  s[i]= *s2++;)
			phone_gen(s, i+1);
	else
		phone_gen(s, i+1);

	s[i] = c;
	}

-------

I guess it also assumes that the characters '2' through '9' are
contiguous in your character set.