Smart keypad 1 problem

#1

can you please suggest the approach for the problem

#2

this problem can be approached using recursive formulation.
say x is our string input and f(x) is our solution. recursive formulation would be:
f(x) = (character set of code of x[0] ) * f(x[1:]), here * is cross product and x[1:] is string x after removing first character.
eg. f(“231”) = (character set of code of ‘2’) * f(“31”)
= (a,b,c) * f(“31”)
this is recursive function as f is written in terms of f.

Now write algorithm for this:
prototype of function, say function name as encode:
public void encode(string x, string res, ArrayList ans){
1.write base condition here //think about base condition
if(base_condition){
ans.add(res);
return ;
}
2. char_code_array = get character array of code of x.charAt(0) // i.e ‘2’ to [a,b,c]
3. for(char c in char_code_array){
encode(x.substring(1), res+c, ans)
}
}

call encode function and ans will contain your final solution.

Thanks.

#3

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