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Questions and Answers
What is the primary purpose of the removeInvalidParentheses function?
What is the primary purpose of the removeInvalidParentheses function?
- To reverse a string.
- To add parentheses to a string.
- To remove the minimum number of invalid parentheses to make the string valid. (correct)
- To count the number of parentheses in a string.
The forward pass in the removeInvalidParentheses function is designed to remove extra opening parentheses.
The forward pass in the removeInvalidParentheses function is designed to remove extra opening parentheses.
False (B)
If the variable open is greater than 0 after the forward pass, what does this indicate about the string?
If the variable open is greater than 0 after the forward pass, what does this indicate about the string?
unmatched opening parentheses
In the backward pass, if a '(' is encountered and there are still unmatched ones to remove, the algorithm will _____ it.
In the backward pass, if a '(' is encountered and there are still unmatched ones to remove, the algorithm will _____ it.
Why is the reverse function used at the end of the removeInvalidParentheses function?
Why is the reverse function used at the end of the removeInvalidParentheses function?
If the input string s is already valid, the function removeInvalidParentheses will modify the string.
If the input string s is already valid, the function removeInvalidParentheses will modify the string.
What data structure is used to build the corrected string in both the forward and backward passes?
What data structure is used to build the corrected string in both the forward and backward passes?
The open variable in the code functions as a _____ to track unmatched opening parentheses.
The open variable in the code functions as a _____ to track unmatched opening parentheses.
Which of the following best describes the algorithm's approach to handling characters that are not parentheses?
Which of the following best describes the algorithm's approach to handling characters that are not parentheses?
The backward pass always removes all opening parentheses from the string.
The backward pass always removes all opening parentheses from the string.
What condition must be met for a closing parenthesis to be added to the result during the forward pass?
What condition must be met for a closing parenthesis to be added to the result during the forward pass?
The algorithm processes the string twice, once from _____ to _____, and then in the _____. direction.
The algorithm processes the string twice, once from _____ to _____, and then in the _____. direction.
What is the space complexity of the removeInvalidParentheses function, assuming the length of the input string is n?
What is the space complexity of the removeInvalidParentheses function, assuming the length of the input string is n?
The primary goal of using two passes (forward and backward) is to optimize time complexity by reducing redundant checks.
The primary goal of using two passes (forward and backward) is to optimize time complexity by reducing redundant checks.
Why doesn't the algorithm need to track lowercase letters during the forward and backward passes?
Why doesn't the algorithm need to track lowercase letters during the forward and backward passes?
The process of skipping extra '(' during the backward pass is crucial for ensuring that the resultant string contains only the _____ parentheses.
The process of skipping extra '(' during the backward pass is crucial for ensuring that the resultant string contains only the _____ parentheses.
Match the pass with its primary function in the removeInvalidParentheses algorithm:
Match the pass with its primary function in the removeInvalidParentheses algorithm:
If an input string contains no parentheses, what will the removeInvalidParentheses function return?
If an input string contains no parentheses, what will the removeInvalidParentheses function return?
The removeInvalidParentheses function can handle multiple types of brackets, such as {} and [].
The removeInvalidParentheses function can handle multiple types of brackets, such as {} and [].
What happens to the open counter when an opening parenthesis '(' is encountered during the forward pass?
What happens to the open counter when an opening parenthesis '(' is encountered during the forward pass?
Flashcards
removeInvalidParentheses Function
removeInvalidParentheses Function
A function that removes the minimum number of invalid parentheses to make the input string valid.
open variable
open variable
Keeps track of unmatched opening parentheses during the forward pass.
result string
result string
The string being built during the forward pass, containing valid characters and parentheses.
Forward Pass
Forward Pass
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Forward Pass Logic
Forward Pass Logic
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Backward Pass
Backward Pass
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finalStr variable
finalStr variable
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Reverse Operation
Reverse Operation
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open == 0
open == 0
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Study Notes
- The function
removeInvalidParenthesesremoves the minimum number of invalid parentheses from a given string to make it valid.
Forward Pass
- Iterates through the input string
scharacter by character - If the character is an opening parenthesis '(', it's added to the
resultstring, and theopencounter increments - If the character is a closing parenthesis ')', it's added to the
resultonly ifopenis greater than 0, which means there's a corresponding opening parenthesis.openis then decremented. - Other characters are directly added to
result - This pass skips extra closing parentheses
Backward Pass
- Executed only if
openis not 0 after the forward pass, indicating there are unmatched '(' - Traverses the
resultstring in reverse - If an opening parenthesis '(' is encountered and there are still unmatched opening parentheses to remove (
open > 0), it's skipped, andopenis decremented. - Otherwise, the character is added to the
finalStr - The
finalStris then reversed to maintain the original order of characters - This pass removes extra opening parentheses from the end
Return Value
- If after the forward pass,
openis 0, it means all parentheses are balanced, so theresultis returned - Otherwise, the corrected
finalStris returned after the backward pass and reversal
Validity
- The solution ensures the final string is valid by removing the minimum number of parentheses
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