Map strings of digits to potential alphanumeric character strings using the T9 telephone keypad.
The keypad on most touch tone telephones and cell phones has a grid of digits (0-9). Most of the digits are also associated with a set of letters:
| digit | characters |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | A B C |
| 3 | D E F |
| 4 | G H I |
| 5 | J K L |
| 6 | M N O |
| 7 | P Q R S |
| 8 | T U V |
| 9 | W X Y Z |
An area code (e.g. 206) can be mapped through the T9 keypad:
| 2 | 0 | 6 |
|---|---|---|
| A | 0 | M |
| B | N | |
| C | O |
to a set of alphanumeric strings:
A0M A0N A0O
B0M B0N B0O
C0M C0N C0O
The basic exercise is to write an algorithm to print all possible mappings
generated by a sequence of digits (e.g. 206) mapped via the T9 keypad.
For example:
206 ->
A0M
A0N
A0O
B0M
B0N
B0O
C0M
C0N
C0O
Given an array of English words, how would you post-process the list of strings generated in the basic step looking for non-overlapping English words. Characters not in an English word would be reverted to digits. For example:
2069936413 -> b0myxdogle -> 20my9dog13