# on 23-Oct-2018 (Tue)

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#### Flashcard 3442072227084

Question
In linux, regular expression [...] , marked via the enclosing escaped-round-bracket syntax, group parts of a regular expression together, so they can be swapped or just displayed in chuncks via sed, for example.
Answer
subexpressions

status measured difficulty not learned 37% [default] 0
8. Streams and sed -- The Stream Editor
g text around within lines. Consider, for example, the output of ls : say you want to automatically strip out only the size column-- sed can do this sort of editing if you use the special  <span>notation to group parts of the regular expression together. Consider the following example: sed -e 's/$$<[^ ]*>$$$$[ ]*$$$$<[^ ]*>$$/\3\2\1/g' Here sed is searching for the expression \<.*\>[ ]*\<.*\> . From the chapter

#### Flashcard 3497609792780

Question
In python/algorithms, what is the time complexity of index lookup/assignment for lists (e.g. you have l = [1,2,3,4,5], what is big-O of doing: l[2] = 0)?
Answer
O(1)
^^ the reason it is O(1), is because doing delete via pop(i) is O(n) as a python tradeoff to make index assignment faster.

status measured difficulty not learned 37% [default] 0

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#### Flashcard 3497613724940

Question
In python/algorithms, what is the time complexity of append for lists (e.g. you have l = [1,2,3,4,5], what is big-O of doing: l.append(6))?
Answer
O(1)

status measured difficulty not learned 37% [default] 0

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#### Flashcard 3497617657100

Question
In python/algorithms, what is the time complexity of pop() for lists (e.g. you have l = [1,2,3,4,5], what is big-O of doing: l.pop()?
Answer
O(1)

status measured difficulty not learned 37% [default] 0

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#### Flashcard 3497621589260

Question
In python/algorithms, what is the time complexity of pop(i) for lists (e.g. you have l = [1,2,3,4,5], what is big-O of doing: l.pop(0)?
Answer
O(n)
^^ this is python sacrifice to make index assignment O(1)

status measured difficulty not learned 37% [default] 0

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#### Flashcard 3497625521420

Question
In python/algorithms, what is the time complexity of insert(i,item) for lists (e.g. you have l = [1,2,3,4,5], what is big-O of doing: l.insert(1,7)?
Answer
O(n)

status measured difficulty not learned 37% [default] 0

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#### Flashcard 3497629453580

Question
In python/algorithms, what is the time complexity of concatination for lists, where original list length is n, and the length of list being concatinated is k?
Answer
O(k)

status measured difficulty not learned 37% [default] 0

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