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Valid Parentheses
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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.
Examples
Example 1
Input
s = "()[]{}"Output
true
Each opening bracket is matched by the same type of closing bracket in the correct order.
Example 2
Input
s = "([)]"
Output
false
The brackets are not closed in the correct order — the '[' is closed by ')' before the '(' is closed.
Example 3
Input
s = "{[]}"Output
true
The '[' inside '{}' is properly closed before the outer '{' is closed.
Constraints
- 1 <= s.length <= 104
- s consists of parentheses only '()[]{}'.
Optimal complexity
Time
O(n)
Space
O(n)
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