CODE 110: 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:

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

public ArrayList<String> generateParenthesis(int n) {// Start typing your Java solution below// DO NOT write main() function// (()) ()()return dfs(0, n, n);}ArrayList<String> dfs(int right, int left, int n) {if (0 == left) {ArrayList<String> results = new ArrayList<String>();String str = "";for (int i = 0; i < n - right; i++) {str += ")";}results.add(str);return results;}ArrayList<String> results = new ArrayList<String>();for (int i = 0; i <= n - left - right; i++) {for (int j = 1; j <= 1; j++) {ArrayList<String> strs = dfs(i + right, left - j, n);for (String str : strs) {for (int k = 1; k <= j; k++) {str = "(" + str;}for (int k = 0; k < i; k++) {str = ")" + str;}results.add(new String(str));}}}return results;}