EasyStacks QueuesFree practice
Valid Parentheses
Asked atgoogleamazonmetamicrosoftbloomberg
01 · Problem
Given a string s containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.
An input string is valid if:
- Open brackets must be closed by the same type of brackets.
- Open brackets must be closed in the correct order.
- Every close bracket has a corresponding open bracket of the same type.
02 · Examples
Example 01
Input
s = "()[]{}"Output
true
Each opening bracket is matched by the same type of closing bracket in the correct order.
Example 02
Input
s = "([)]"
Output
false
The brackets are not closed in the correct order — the '[' is closed by ')' before the '(' is closed.
Example 03
Input
s = "{[]}"Output
true
The '[' inside '{}' is properly closed before the outer '{' is closed.
03 · Constraints
- 011 <= s.length <= 104
- 02s consists of parentheses only '()[]{}'.
04 · Optimal complexity
- Time
- O(n)
- Space
- O(n)
05 · Two ways to work on it
Practice it alone or rehearse it as an interview.
Practice Mode gives you an editor and test runs, nothing else. AI Interview Mode puts a voice interviewer on the other side, adds a clock, and ends with a scored summary of the round.