题解 | #括号生成#

递归的使用

class Solution {
  public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param n int整型 
     * @return string字符串vector
     */
    vector<string> generateParenthesis(int n) {
      if (n == 0) {
        return std::vector<std::string>();
      }
      
      std::string tmp;
      std::vector<std::string> str;
      
      recursion(0, 0, n, str, tmp);
      
      return str;
    }
  private:
    void recursion(int left, int right, const int &n, std::vector<std::string> &str, std::string tmp) {
      if (left == n && right == n) {
        str.push_back(tmp);
        return ;
      }
      
      if (left < n) {
        recursion(left + 1, right, n, str, tmp + '(');
      }
      
      if (right < left && right < n) {
        recursion(left, right + 1, n, str, tmp + ')');
      }
    }
};