leetcode 22. 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:

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

解：本题的思路是利用二叉树的想法来遍历所有的情况，采用深度优先的搜索算法dfs。而二叉树的本质就是利用递归，主要想好添加左括号和右括号的条件。

class Solution {public:    vector<string> generateParenthesis(int n) {        vector<string> res;        addingChar(res, "", n, n);        return res;    }    void addingChar(vector<string> &res, string str, int left, int right){        if(left == 0 && right == 0){            res.push_back(str);return;        }        if(left > 0){            addingChar(res, str+"(", left - 1, right);        }        if(right > left){            addingChar(res, str+")", left, right - 1);        }    }};