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Computer Science: The Good Parts Jeffrey Cohen
 @jeffcohen jeffcohenonline.com

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Data Structures

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Data Structures

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Linked List

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60 31 5 45 80 70 74 99 87 68 Binary Tree

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Data Structures

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Graph

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Algorithms

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Babbage and Lovelace

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Apollo 11

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Margaret Hamilton Source code of the Apollo Guidance Computer

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Complexity A "green" test suite is not an indicator of sustainability. Some implementations are more complex than others. • Time • Space

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O(n) def exists?(name_to_find, names) names.each do |name| return true if name == name_to_find end return false end

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def exists?(name_to_find, names) names.each do |name| return true if name == name_to_find end return false end O(n) 0 100 200 300 O(n)

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O(log n) def exists?(name_to_find, sorted_names) 
 
 midpoint = sorted_names.length / 2 
 return true if sorted_names[midpoint].name == name_to_find 
 if name < sorted_names[midpoint].name 
 search(name_to_find, sorted_names[0, midpoint]) 
 else 
 search(name_to_find, sorted_names[midpoint, -1]) 
 end 
 return false
 end

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def exists?(name_to_find, sorted_names) 
 
 midpoint = sorted_names.length / 2 
 return true if sorted_names[midpoint].name == name_to_find 
 if name < sorted_names[midpoint].name 
 search(name_to_find, sorted_names[0, midpoint]) 
 else 
 search(name_to_find, sorted_names[midpoint, -1]) 
 end 
 return false
 end O(log n) 0 100 200 300 O(log n) O(n)

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Atom.io blog post

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O(n2) def make_combinations(items) items.map do |item| items.map { |inner_item| [item, inner_item] } end end [1,2,3] => [[1,1], [1,2], [1,3], [2, 1], [2, 2], [2, 3], [3, 1], [3, 2], [3, 3]]

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O(n2) def make_combinations(items) items.map do |item| items.map { |inner_item| [item, inner_item] } end end 0 100 200 300 O(n2) O(n) O(log n)

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The Future

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Alan Turing

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Alan Turing Computer science
 is not
 computer programming

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Alan Turing It's a way of thinking

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Grace Hopper

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Grace Hopper

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Grace Hopper Humans are allergic to change. They love to say, "We've always done it this way." I try to fight that.
 
 That's why I have a clock on my wall that runs counter-clockwise.

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Grace Hopper A ship in port is safe; but that is not what ships are built for. Sail out to sea and do new things.

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Questions? Thoughts? Find me on twitter
 @jeffcohen
 
 
 jeffcohenonline.com