Generate Parentheses (Java)

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:

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




Solution: Greedy and Recursive

Take advantage of the feature of parentheses, left side and right side must match each other,  in other words, if there a left side parenthese,  whatever position it is, there must be a right side parenthese to match it.