C#/Java solution for Leetcode question: Generate Parentheses (difficulty : medium)

Source:

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:

[
"((()))",
"(()())",
"(())()",
"()(())",
"()()()"
]

My C#/Java solution is here:

https://github.com/jiajionline/LeetcodeSolutionWithMultipleLanguages/tree/master/Generate%20Parentheses