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:

[

  "((()))",

  "(()())",

  "(())()",

  "()(())",

  "()()()"

]

来源：力扣（LeetCode）

链接：https://leetcode-cn.com/problems/generate-parentheses

著作权归领扣网络所有。商业转载请联系官方授权，非商业转载请注明出处。

【Leet Code】22. Generate Parentheses_字符串

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

【Leet Code】22. Generate Parentheses_字符串指针_02

传字符串，变成传字符串指针，节约了一半时间

class Solution {
public:
    vector<string> generateParenthesis(int n) {
      vector<string> result;
      string temp = "";
      dfsGP(result, temp, n, n, n);
      return result;
    }
    void dfsGP(vector<string>& result, string& cur, int n, int lN, int rN) {
      if (!lN) {
        for (int i = 0; i < rN; ++i)
          cur.push_back(')');
        result.push_back(cur);
        for (int i = 0; i < rN; ++i)
                    cur.pop_back();
      }
      else {
                cur.push_back('(');
        dfsGP(result, cur, n, lN - 1, rN);
                cur.pop_back();
        if (rN > lN) {
                    cur.push_back(')');
          dfsGP(result, cur, n, lN, rN - 1);
                    cur.pop_back();
        }
      }
    }
};

【Leet Code】22. Generate Parentheses_字符串_03