Sorry - I'm not able to understand the post. I fully understand the problem - I ask this question sometimes during interviews - with two bracket characters. Say, () and []. So a string like "([)]" is not correctly balanced.

Some folks try with counters - but that very quickly gets out of hand. I try to prod them to a solution - by giving patterns that will defeat their solutions.

What I'm expecting is that the person can identify that use of stack here, which (and this is my source of confusion here) - is the most natural way to solve this problem. Push when we encounter an opening bracket, pop and match when we encounter a closing bracket. The function is generic, within 10 lines in C, can easily be extended to more bracket characters.

So - what is the point of this post?