Identify matching-opener problems
Updated
Signals: nested delimiters, closest unmatched, HTML tags, function calls, path '..' with directories. Recipe: push openers, pop on closers, empty at end. Not every string problem is this. Palindromes are two pointers.
What to focus on
If mismatch depends on nearest still-open item, it is a stack. If it depends on counts only (even number of parens, no types), a depth integer may suffice.
Worked examples
yes types
s = "([])"- nearest opener
Result: stack
maybe depth
s = "(())" one type- depth integer enough for validity
- stack still ok
Result: depth or stack
no
s = "abca" palindrome- ends vs center
- not nested openers
Result: two pointers
Try it
Write classifyOpener(s). s is a string representing the pattern. Return "stack", "depth", or "twoPointers". Matching-opener vs depth vs not a stack problem. s = \"([])\" → stack. s = \"(())\" one type → depth or stack. s = \"abca\" palindrome → two pointers.
Each string is a representative of its pattern, not a malformed leftover. Classify the structure.