LeetCode Generate Parentheses

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) {
        vector<string> ret;
    	bool* result = new bool[2*n];
		dfs(ret, result, 0, 2*n);
		delete result;
        return ret;
    }

	void dfs(vector<string>& ret, bool result[], int cur, int n)
	{
		if(cur == n)
		{
			int leftCnt = 0;
			stringstream oss;
			for(int i = 0; i < n; ++i)
			{
				leftCnt += (result[i])? 1: -1;
				if(leftCnt < 0 || leftCnt > n/2)
					break;
				oss << (result[i]? '(': ')');
			}

			if(0 == leftCnt && oss.str().size() == n)
				ret.push_back(oss.str());
		}
		else
		{
			result[cur] = true;
			dfs(ret, result, cur+1, n);
			result[cur] = false;
			dfs(ret, result, cur+1, n);
		}
	}
};