[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:
"((()))", "(()())", "(())()", "()(())", "()()()"
想到的就是DFS,backtrace
class Solution { vector<string> m_strs; public: void backtrace(string str, int leftPaNum, int paNum) { if(leftPaNum == paNum && str.size() == 2*paNum) { m_strs.push_back(str); return; } if(leftPaNum == paNum) { str += ")"; backtrace(str, leftPaNum, paNum); } else { // left num == right num if(leftPaNum == (str.size()-leftPaNum) ) { str += "("; backtrace(str, leftPaNum + 1, paNum); } else// left num > right num { str += "("; backtrace(str, leftPaNum + 1, paNum); str.erase(str.end() - 1); str += ")"; backtrace(str, leftPaNum, paNum); } } } vector<string> generateParenthesis(int n) { m_strs.clear(); string str; backtrace(str, 0, n); return m_strs; } };