给出 n 代表生成括号的对数，请你写出一个函数，使其能够生成所有可能的并且有效的括号组合。
例如，给出 n = 3，生成结果为：
[ "((()))", "(()())", "(())()", "()(())", "()()()" ]
class Solution { public List<String> generateParenthesis(int n) { List<String> ans = new ArrayList(); backtrack(ans, "", 0, 0, n); return ans; } public void backtrack(List<String> ans, String cur, int open, int close, int max){ if (cur.length() == max * 2) { ans.add(cur); return; } if (open < max) backtrack(ans, cur+"(", open+1, close, max); if (close < open) backtrack(ans, cur+")", open, close+1, max); } }
原文：https://www.cnblogs.com/JAYPARK/p/10453241.html