一、题目内容

二、题解

解法1：

思路

代码

public class Solution {
    ArrayList<String> ans = new ArrayList<>();
    public ArrayList<String> generateParenthesis (int n) {
        // write code here
        recur(n,0,0,"");
        return ans;
    }
    private void recur(int n,int left,int right,String cur){
        if(left>n||right>left){
            return;
        }
        if(left==n&&right==left){
            ans.add(cur);
            return;
        }
        recur(n,left+1,right,cur+"(");
        recur(n,left,right+1,cur+")");
    }
}