Transcript Nifty Assignments - UT Computer Science

Nifty Assignments
Shamelessly Borrowed from Nick
Parlante at Stanford University
A Little History
• Began as a small panel
discussion at SIGCSE
in 1999
• Friends of Nick Parlante
would present cool assignments
• Now the “800 pound gorilla” of SIGCSE
• original web site
– nifty.stanford.edu/
– AP Central has a similar page
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Start With the Problem
• Greg Lavender
- “Start with the Problem”
• Motivate what needs to
be learned with
an interesting problem
• Biology teacher I knew started his year with the
question “What is food?”
• I think CS actually has it easy because we can
actually solve interesting problems in our labs.
– students get immediate feedback and can create non
trivial artifacts
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What Makes an Assignment Nifty?
• Not the same answer for everyone
• I think determining if a 400 digit number is
prime is an a very interesting problem
– algorithmically interesting with many
approaches
– look at efficiency of solutions
– data representation is interesting
– relevant -> Encryption techniques such as
RSA
• A lot of my students DON’T find this as
interesting as I do
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What Makes an Assignment Nifty?
• they are fun, playful, interesting
• they are often, but not always visual.
• they are scalable. Top students can run with
them, others can complete the basics
• they fulfill Astrachan’s Law
• Owen Astrachan –
“Do not given an assignment
that computes something
that is more easily figured
out without a computer such
as the old Fahrenheit / Celsius
conversion problem.”
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Example 1 – Name Surfer
• From Nick P.
• The Name Surfer
• Social Security Administration
“popular baby names” web site.
• www.ssa.gov/OACT/babynames/
• Data on names of children born in US
• Assignment uses list of 1000 most popular
names by decade stored in a text file
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Name Surfer
• Students must read in and store the names, search the
names, and complete a GUI to show the names
Where did all
the Ethels go?
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Name Surfer
• Handout has fairly detailed step by step
instructions on how to approach the problem
• Components
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modular design
multiple classes
using ArrayLists and other classes
calculations for lines on display
• Scalable
– do simple text based, then add window, then add GUI
– don’t provide data file, have students create it from
multiple files
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Name Surfer
• Use the tool you have created to
investigate naming trends
– plot grand parents names
– Rock, Trinity, Dwight
– Jose, Mohammed
– Mike and Michael, Dave and David, Matt and
Matthew
– J, D, M
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Example 2 – Word Ladders
• Proposed by Owen Astrachan
• Begin with two 5 letter words and a list of
valid 5 letter words:
– brain, smart
• Change one letter of start word for next word
• New word be in the list of valid words
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Word Ladder
smart
scart (a type of audio / video connector)
scant
slant
plant
plait
plain
blain (an inflammatory swelling or sore)
brain
• My word list was derived from a Scrabble
word list.
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Word Ladder
• Actually exploring a graph
• the nodes are the words
• connections (or edges or links) exist between
2 words if they differ by a single letter
smarm
start
swart
smart
scant
scart
smalt
scare
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Word Ladder Assignment
• I present an algorithm to students that
does a breadth first search of the graph
using a queue of stacks
• Students must implement the stack and
queue classes and then implement the
algorithm
• Components
– implementing data structures
– implementing algorithms
– comparisons of efficiency
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Word Ladder Assignment
• How do you find words one letter different?
• do a linear search of all words in the word list
– O(N)
• …but the word list is sorted.
• Given a word generate all possible 5 letter
combinations that are one letter different
– smart -> amart, bmart, cmart, … smarx, smary, smarz
(125 in all)
– take these 125 words and search the word list for
each one using a binary search
– This can’t be faster can it?
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Word Ladders
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smart to brain
Linear search method – 0.991 seconds
Binary search method – 0.260 seconds
How can that be?
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Word Ladders
• Another extension
– Do a depth first search
•
•
•
•
Ladders are much longer
smart – brain, 521 words in 0.140 seconds
The word list has about 8500 words
Other possible extensions:
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start from both ends and work towards the middle
find all the connections up front
don’t provide the words in sorted order
map out all the independent sections, which is the biggest?
which word is closest to the center of the largest graph?
what is the largest ladder that exists?
other rules from Wikipedia
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