But I needed to write something to parse a file of brackets for syntax highlighting.

There are probably millions of implementations of this, millions of which are better than mine. So be it, because C++ can be fun to write in.

open_node indicates an opening bracket. It adds a child to the current bracket and recursively starts again.

closed_node indicates a closing bracket. It marks the current node as closed, and returns to the parent.

Both return a pointer to a parse_node which indicates the current state of the parsing tree.

Code to parse a list of booleans giving open or close:

int main () {
    parse_node *current = new parse_node((parse_node *)0);
    
    std::vector<bool> bracks = {1, 0, 1, 0};
    
    for (bool b : bracks) {
        if (b) current = current->open_node();
        else current = current->close_node();
    }
}

This algorithm is O(n) for both parsing and deletion.

10³μs = 1ms, 10⁶μs = 1s

Parsing ((())()(()

By hand, we can also get the answer of

(
    (
        (
        )
    )
    (
    )
    (
    	(
        )