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);
}
}
};