find all possible words based on phone numbers

This is a classic code problem:

http://www.geeksforgeeks.org/find-possible-words-phone-digits/

This can be done beautifully in a recursion approach. The key here is to loop through all digits in the phone number from left to right, set the corresponding char in the word based on the phone keyboard, the recursion will terminate when the last digit is passed.


Another approach is to do it iterativelly. The key here is to find a way to calculate next word from a current word. for example, if the current word is ADG, then next word is ADH, next after that is ADI, AEG.