leetcode-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:

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




class Solution {public:    vector<string> generateParenthesis(int n) {        // IMPORTANT: Please reset any member data you declared, as        // the same Solution instance will be reused for each test case.        if(n == 0) {            return vector<string>(1, "");        }        if(n == 1) {            return vector<string>(1, "()");        }        vector<string> left;        vector<string> right;        vector<string> svec;        int i = 0, j = 0, k = 0;        string str;        for(k = n - 1; k >= 0; --k) {            left = generateParenthesis(k);            right = generateParenthesis(n - 1 - k);            for(i = 0; i < left.size(); ++i) {                for(j = 0; j < right.size(); ++j) {                    str.clear();                    str.append("(");                    str.append(left[i]);                    str.append(")");                    str.append(right[j]);                    svec.push_back(str);                }            }        }        return svec;    }};

这个递归有点麻烦