Algorithm to generate all combinations of a string

Question

I found a link online that shows an algorithm to generate all combinations of a string: http://www.mytechinterviews.com/combinations-of-a-string

Algorithm is copied belo

Answer 1

It fits very logically. You see what we have here is a recursive algorithm. At each step in position i we put a letter of the string then call the function recursively to put another letter on the next position. However, when we return from recursion, we need to remove the character we put initially, so that we can replace it with the next possible one in the sequence. Example:

append a on pos 0 -> a
call recursion
append a on pos 1 -> aa
call recursion
append a on pos 2 -> aaa
return from recursion
remove a from pos 2 -> aa
append b on pos 2 -> aab
return from recursion
remove b from pos 2 -> aa
append c on pos 2 -> aac
etc.