Given N pairs of parentheses, write a function to generate all combinations of well-formed parentheses.

Example: N = 3 -->
[
  '((()))',
  '(()())',
  '(())()',
  '()(())',
  '()()()'
]

Test set 1

Result:

Test set 2

Result:

Test set 3

Result:

Test set 4

Result: