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:

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

public class Solution {    private ArrayList
    
      rel= new ArrayList
     
      ();        public ArrayList
      
        generateParenthesis(int n) {        // Start typing your Java solution below        // DO NOT write main() function                rel.clear();        char[] arr = new char[2*n];        genCur(2*n,n,0,0, arr);        return rel;    }        private void genCur(int sz, int left, int right, int level, char[] arr) {        if(level == sz) {            rel.add( new String(arr) );            return;        }                if(left>0) {            arr[level] = '(';            genCur(sz,left-1, right+1, level+1, arr);        }                if(right>0) {            arr[level] = ')';            genCur(sz,left, right-1, level+1, arr);        }    }}