Given pairs of parentheses, generate all combinations of well-formed parentheses.
Example: For , return ["((()))","(()())","(())()","()(())","()()()"]. The number of valid combinations is the th Catalan number.
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Given pairs of parentheses, generate all combinations of well-formed parentheses.
Example: For , return ["((()))","(()())","(())()","()(())","()()()"]. The number of valid combinations is the th Catalan number.