Given a keypad as shown in the diagram, and an N digit number which is represented by array a[ ], the task is to list all words which are possible by pressing these numbers.
Example 1:
Input: N = 3, a[] = {2, 3, 4}
Output:
adg adh adi aeg aeh aei afg afh afi
bdg bdh bdi beg beh bei bfg bfh bfi
cdg cdh cdi ceg ceh cei cfg cfh cfi
Explanation: When we press 2,3,4 then
adg, adh, adi, ... cfi are the list of
possible words.
Example 2:
Input: N = 3, a[] = {3, 4, 5}
Output:
dgj dgk dgl dhj dhk dhl dij dik dil
egj egk egl ehj ehk ehl eij eik eil
fgj fgk fgl fhj fhk fhl fij fik fil
Explanation: When we press 3,4,5 then
dgj, dgk, dgl, ... fil are the list of
possible words.
Your Task:
You don't need to read input or print anything. You just need to complete the function possibleWords() that takes an array a[ ] and N as input parameters and returns an array of all the possible words in lexicographical increasing order.
Expected Time Complexity: O(4^{N}^{ }* N).
Expected Auxiliary Space: O(N).
Constraints:
1 ≤ N ≤ 10
2 ≤ a[i] ≤ 9

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