LeetCode #22 Generate Parentheses

Question

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

For example, given n = 3, a solution set is:

[  "((()))",  "(()())",  "(())()",  "()(())",  "()()()"]

Solution

Approach #1

class Solution {    func generateParenthesis(_ n: Int) -> [String] {        var results: [String] = []        func parenthesisStrings(_ str: String, _ open: Int, _ close: Int) {            if open == 0, close == 0 {                results.append(str)                return            }            if open > 0 {                parenthesisStrings(str + "(", open - 1, close)            }            if close > open {                parenthesisStrings(str + ")", open, close - 1)            }        }        parenthesisStrings("", n, n)        return results    }}

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