开始刷leetcode day20：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:

"((()))", "(()())", "(())()", "()(())", "()()()"

Java:

public class Solution {
    public ArrayList<String> generateParenthesis(int n) {
        
        ArrayList<String> list = new ArrayList<String>();
        generate("",0,0,list,n);
        return list;
    }
    
    public void generate(String current, int left, int right,ArrayList<String> list, int n)
    {
        if(left < right) return;
        if(left == n && right == n)
        {
            list.add(current);
            return;
        }else if(left==n)
        {
            generate(current+")",left,right+1,list,n);
            return;
        }
            generate(current+"(",left+1,right,list,n);
            generate(current+")",left, right+1,list,n);
            return;
        
    }
}