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Nice work, you have working algorithms, but some inefficiencies, take a look at my comments and let me know if you have questions.

raise NotImplementedError, "Method not implemented"
return s if s.length == 0
last = s[-1]
s = s[0..-2]

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This creates a new string which increases the time and space time complexity.

So the time and space complexity is O(n^2).

# Time complexity: ?
# Space complexity: ?
# Time complexity: O(n) where n is the length of the string
# Space complexity: O(1)

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Space complexity will be O(n) since you end up using the system stack.


# Time complexity: ?
# Space complexity: ?
def reverse_helper(s, first_index, last_index)

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👍

def nested(s)
raise NotImplementedError, "Method not implemented"
return true if s == ""
return false if !s.include?("(")

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This isn't a good idea since it goes through the entire length of the string. That means your algorithm is O(n^2).

Instead just check the 1st and last character.


# Time complexity: ?
# Space complexity: ?
# Time complexity: O(n) where n is the length of the array

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👍

raise NotImplementedError, "Method not implemented"
return true if s.empty?
if s[0] == s[-1]
s.sub!(s[0], "")

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sub is an O(n) algorithm, so this is an O(n) operation you are doing n times so the full algorithm is O(n^2) for both time and space complexity.

Instead think about tracking the left and right indexes adjusting them each recursive call.

# Space complexity: ?
# Time complexity: O(n) where n is the lenght of the smaller number
# Space complexity: O(1) because there's no variable storing the values of the numbers
def digit_match(n, m)

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👍

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2 participants