leetcode-Generate Parentheses

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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:

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

解题思路

从左到右生成相应的符号序列，首先添加‘（’，左右括号成对出现且个数一致，右边括号计数大于左边括号时需要添加‘）’，直到计数都为0时表示当前生成一个有效的序列，依次递归操作

class Solution(object):
    def generateParenthesis(self, n):
        """
        :type n: int
        :rtype: List[str]
        """
        def gernerate_str(sstr,lnum,rnum,result=[]):
            if lnum==0 and rnum==0:
                result.append(sstr)
                return
            if lnum>0:
                gernerate_str(sstr+'(',lnum-1,rnum,result)
            if rnum>lnum:
                gernerate_str(sstr+')',lnum,rnum-1,result)
        result=[]
        gernerate_str('',n,n,result)
        return result

发表于：leetcode

2017-04-16

# leetcode