[LeetCode 解题报告]022. 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:

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

考察：生成配对的括号，回溯法。

class Solution {
public:
    vector<string> generateParenthesis(int n) {
        vector<string> res;
        generateParenthesisDFS(n, n, "", res);
        return res;
    }
    
    void generateParenthesisDFS(int left, int right, string out, vector<string> &res) {
        if (left > right) // 放置出现')))((('
            return ;
        if (left == 0 && right == 0)
            res.push_back(out);
        else {
            if (left > 0)
                generateParenthesisDFS(left-1, right, out+'(', res);
            if (right > 0)
                generateParenthesisDFS(left, right-1, out+')', res);
        } 
    }
    
};

完，