Validate Nested Parentheses, Brackets, and Braces

A closing bracket must match the most recent opening bracket that has not yet been closed. Every opening bracket must eventually be closed.

Constraints & Assumptions

• This practice version uses the standard six-character bracket alphabet.
• s may be empty; an empty string is valid.
• The input contains at most 100,000 characters. This is a practice bound for choosing a linear algorithm.
• Adjacent complete groups are allowed: ()[]{} is valid.
• Matching bracket counts alone are insufficient: ([)] is invalid.

Examples

• Input: "{[()]}[]". Output: true. Both the nested group and the final pair close in the correct order.
• Input: "([)]". Output: false. The ) appears while [ is still the most recent unmatched opener.

Clarifying Questions to Ask

• Does the alphabet contain only brackets, or must other characters be ignored or rejected?
• Is the empty string valid?
• Is the input available at once, or must the same check work incrementally over chunks?