[LeetCode] Generate Parentheses

最新推荐文章于 2018-02-24 19:45:54 发布

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最新推荐文章于 2018-02-24 19:45:54 发布

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原文链接：http://www.cnblogs.com/jcliBlogger/p/4573496.html

本文介绍了一种递归算法，用于生成所有可能的有效括号组合。该算法通过递归地添加开括号和闭括号，并确保任何时候闭括号的数量不超过开括号的数量来实现。

Well, there are two ways to add a open or close parenthesis to the current string.

If number of ( is less than n, you can add (;
If number of ) is less than number of (, you can add ).

Maintain a res for all the possible parenthesis and a temporary string sol for the current answer. Now we have the following code.

 1 class Solution {
 2 public:
 3     vector<string> generateParenthesis(int n) {
 4         vector<string> res;
 5         string sol;
 6         genParen(sol, 0, 0, n, res);
 7         return res;
 8     }
 9 private:
10     void genParen(string& sol, int open, int close, int total, vector<string>& res) {
11         if (open == total && close == total) {
12             res.push_back(sol);
13             return;
14         }
15         if (open < total) {
16             sol += '(';
17             genParen(sol, open + 1, close, total, res);
18             sol.resize(sol.length() - 1);
19         }
20         if (close < open) {
21             sol += ')';
22             genParen(sol, open, close + 1, total, res);
23             sol.resize(sol.length() - 1);
24         }
25     }
26 };