【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:
"((()))", "(()())", "(())()", "()(())", "()()()"
用递归生成所有的括号组合,并且在递归过程中不断剪枝
剪枝的条件:
leftNum>n||rightNum>n||rightNum>leftNum)
1.左、右括号数目大于了n
2.右括号数目大于了左括号数目
1 class Solution { 2 3 public: 4 5 vector<string> generateParenthesis(int n) { 6 7 8 9 vector<string> result; 10 11 generate(result,"",0,n,0,0); 12 13 return result; 14 15 16 17 } 18 19 20 21 void generate(vector<string> &result,string tmp,int index,int &n,int leftNum,int rightNum) 22 23 { 24 25 if(leftNum>n||rightNum>n||rightNum>leftNum) 26 27 { 28 29 return; 30 31 } 32 33 if(index==2*n) 34 35 { 36 37 result.push_back(tmp); 38 39 return; 40 41 } 42 43 44 45 generate(result,tmp+"(",index+1,n,leftNum+1,rightNum); 46 47 generate(result,tmp+")",index+1,n,leftNum,rightNum+1); 48 49 } 50 51 };