题解 | #括号生成#

class Solution {
public:
    void dfs(vector<string>&ans,string&temp,int n,int l,int r)
    {
        if(l+r==n)
        {
            if(l==r)ans.push_back(temp);
            return;
        }
        if(l==r)
        {
            temp.push_back('(');
            dfs(ans,temp,n,l+1,r);
            temp.pop_back();
        }
        else
        {
            temp.push_back('(');
            dfs(ans,temp,n,l+1,r);
            temp.pop_back();
            temp.push_back(')');
            dfs(ans,temp,n,l,r+1);
            temp.pop_back();
        }
    }
    vector<string> generateParenthesis(int n) {
        vector<string>ans;
        string temp="";
        dfs(ans,temp,2*n,0,0);
        return ans;
    }
};