LintCode 生成括号

原题

样例

n = 3

"((()))", "(()())", "(())()", "()(())", "()()()"

解题思路

代码实现

class Solution:
# @param {int} n n pairs
# @return {string[]} All combinations of well-formed parentheses
def generateParenthesis(self, n):
# Write your code here
self.limit = n
self.ret = []
self._generateParenthesis("", 0, 0)
return self.ret

def _generateParenthesis(self, comb, leftnum, rightnum):
if leftnum == self.limit and rightnum == self.limit:
self.ret.append(comb)
return
if leftnum < self.limit:
self._generateParenthesis(comb+'(', leftnum+1, rightnum)
# 如果右括号小于左括号才可以加右括号
if rightnum < leftnum:
self._generateParenthesis(comb+')', leftnum, rightnum+1)