LeetCode22：Generate Parentheses

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:

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

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LeetCode：链接

如果左括号还有剩余，则可以放置左括号，如果右括号的剩余数大于左括号，则可以放置右括号。

class Solution(object):
    def generateParenthesis(self, n):
        """
        :type n: int
        :rtype: List[str]
        """
        if n == 0:
            return []
        res = []
        self.generate(n, n, "", res)
        return res

    # left是左括号的数量 right是右括号的数量 pStr是一个合法的括号组合
    def generate(self, left, right, pStr, res):
        if left == 0 and right == 0:
            res.append(pStr)
            return
        # 如果左括号还有剩余，则可以放置左括号
        if left > 0:
            self.generate(left-1, right, pStr+"(", res)
        # 如果右括号的剩余数大于左括号，则可以放置右括号
        if right > left:
            self.generate(left, right-1, pStr+")", res)