Longest Valid Parentheses
HardDynamic ProgrammingDynamic Programming
Solve this the way you would in the interview: out loud, on a timer, with an AI interviewer asking follow-ups while you code. You get a scored report at the end.
Practice this as a mock interviewFree to start, no account neededProblem
Given a string containing just the characters ( and ), return the length of the longest valid (well-formed) parentheses substring.
Examples
Input: s = "(()"
Output: 2
The longest valid parentheses substring is "()".
Input: s = ")()())"
Output: 4
The longest valid parentheses substring is "()()".
Input: s = ""
Output: 0
Constraints
- 0 <= s.length <= 3 * 10^4
- s[i] is '(' or ')'.
What the interviewer grades
A correct solution is one of five scores. The report also grades problem understanding (did you clarify inputs and edge cases before coding), problem solving, communication while you work, code quality, and testing. See a sample report, or read up on the pattern in the lessons.