phone numbers

It has become quite common these days for businesses to associate their telephone numbers with words that people can remember more easily. For example, Sears Canada's catalogue number is: 1-800-26-SEARS.

The digits 2-9 on a telephone key pad are each associated with three letters of the alphabet:

2	A-B-C	6	M-N-O
3	D-E-F	7	P-R-S
4	G-H-I	8	T-U-V
5	J-K-L	9	W-X-Y

Notice that the digits 1 and 0 do not have letters associated with them. Notice also that only 24 letters are represented. The letters Q and Z are not in the table.

Your job is to write a program that will take a 7-digit phone number and generate a list of possible words that can be associated with it using a standard mapping of digits to letters. Since there are 3 possible letters for each digit, for a 7-digit number, there are approximately 3⁷ = ~2200 possibilities. If you also include 6-letter words, there are an additional 3⁶ = ~725 (assuming you only choose on the last 6 digits and not the first). There are ~250 5-letter words and finally ~80 4-letter words (assuming again you only check the rightmost digits). This makes a grand total of 3250 different combinations.

This is a very long list. In order to keep the output to this program manageable, let's look only for 5-letter words. This would leave the first 2 digits of the number in their "raw" state. Even then, we should be able to eliminate a fair number of these using a few simple approaches:

1. Any 'word' produced (mapping) that does not contain a vowel can be eliminated since it is unlikely to be a word.

2. Any phone number that contains a 1 or 0 anywhere in the 5-digit 'target zone' can't be converted.

Even with the ability to eliminate a fair number of candidates, the list is likely to be quite long. Make sure you format you output to print more than one phone-word per line.

When you run your program, re-direct output to a file so you don't need to see all the output.

If you are doing more than 5-digits DO NOT print the entire output file!!!! Instead use UNIX's 'head' and 'tail' commands to display the first and last 50-100 lines.

BONUS:

1. Allow the user to choose which 5-digit 'set' to use in the search (include the option 'ALL'). [i.e. start with digit 3: ddd-dddd -> ddL-LLLL]
2. Allow the user to try more than one number (one after the other).
3. Allow the user to choose a range for the word size (i.e. 7-letter through 4-letter words - include the option 'ALL')
4. Sort the output in alphabetical order.
5. Check the output against the system's spell-checker ('spell') and eliminate non-words. Create a shell script for this.

Updated: August 10, 2005 09:56 AM