It depends on the problem definition (specifically on the definition of the word "brackets"). If you want to ensure the proper balancing of all of {}, [], and (

It depends on the problem definition (specifically on the definition of the word "brackets"). If you want to ensure the proper balancing of all of {}, [], and () [while excluding improper nesting], you need a stack [or equivalent]. If you only want to ensure () balancing, you can just do a count. IMO: ({[]}) // has balanced brackets ({[}]) // has imbalanced brackets