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Valid Parentheses
Given a string s containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.
A string is valid if:
- Open brackets are closed by the same type of brackets.
- Open brackets are closed in the correct order.
- Every close bracket has a corresponding open bracket of the same type.
The empty string is considered valid.
Examples
Constraints
- 0 <= s.length <= 10^4
- s consists of parentheses only '()[]{}'.
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Your approach
- Pattern:Stack
- Time:O(N)
- Space:O(1)
Complete approach — pattern and complexity both named.
Coach
What you got right
You correctly matched the sorted input requirement and implemented a linear-time scan using two pointers.
Where it diverged
No divergence detected. The code correctly aligns with the stated approach.
Next attempt: focus on
Try solving related sliding window problems to build familiarity with two-pointer variants.
Signals
No signals fired — clean run, you stayed in flow.