LeetCode in Elixir
22. Generate Parentheses
Medium
Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses.
Example 1:
Input: n = 3
Output: [”((()))”,”(()())”,”(())()”,”()(())”,”()()()”]
Example 2:
Input: n = 1
Output: [”()”]
Constraints:
1 <= n <= 8
Solution
defmodule Solution do
@spec generate_parenthesis(n :: integer) :: [String.t()]
def generate_parenthesis(n) do
generate("", n, n, [])
end
defp generate(current, 0, 0, acc) do
[current | acc]
end
defp generate(current, open, close, acc) when open > 0 do
acc = generate(current <> "(", open - 1, close, acc)
if open < close do
generate(current <> ")", open, close - 1, acc)
else
acc
end
end
defp generate(current, _open, close, acc) when close > 0 do
generate(current <> ")", 0, close - 1, acc)
end
end