Question

Hi I have 2 questions
1- Is there a way to search this site for answers to previous questions?
2 - I don't understand the following in Problem set 6 from fall 2008,

Now, given a hand, here's how to use that dict to find a word that can be made from that hand:
To find some word that can be made out of the letters in HAND:
For each subset S of the letters of HAND:
Let w = (string containing the letters of S in sorted order)
If w in d: return d[w]

Are we being asked to test every possible subset of letters from the HAND?
What is the best way to generate a full set of these subsets?

Answer 1

Exercise 12.4 in thinking in python looks similar - maybe thats my way forward

Answer 2

The generally accepted method for searching this site for past questions is with google. In the search box you will type "keywords I'm looking for site:openstudy.com" to limit the results to OpenStudy.

Answer 3

"Are we being asked to test every possible subset of letters from the HAND? " - yes, combinations if using the 'sorted dictionary' and permutations if not.

"What is the best way to generate a full set of these subsets?"
itertools Combinatoric generators: http://docs.python.org/2.7/library/itertools.html

Answer 4

Thanks for your answers. I wanted to think about how the professors envisaged we would answer the questions, so I wanted to use methods covered in the lectures and readings. I feel I learned the most from the exercises and it has certainly exposed some misundersandings on my part.
I couldn't figure out a neat way to do this. The best I could come up with was to use binary sequences, but would the professors expect the students to do this given that its 6 lectures into an introductory course.
anyway here is my solution

import math
#Test Hand
hand = ['a','b','c','d','e','f','g']
hand_size = 7
#the number of possible subsets is 2^^hand_size -1
#perhaps small benefit in counting backwards from 1111111 to 0000001
#don't need to consider 0000000
for count in range(pow(2,hand_size)-1,1,-1):
#convert each count to a binary string
bin_index = bin(count)
# format the string remove the leading '0b'
# pad with 0 so each string is hand_size chars
# convert string to list
bin_list = list(bin_index[2:].zfill(hand_size))
# create a tuple, esch element is a character from the binary list and the hand e.g (1, 'a')
t=zip(bin_list, hand)
subset = [] # initialise / empty the subset
for index, letter in t:
#if 1 in binary sequence add character to the subset
if index == '1':
subset.append(letter)
print count, subset

Answer 5

please use a code pasting site:

- http://dpaste.com
- http://pastebin.com
- https://gist.github.com/
- http://pastie.org
- http://codepad.org
- http://ideone.com
- http://www.repl.it/

paste your code there and post the link here. select Python syntax highlighting when u paste.

Answer 6

does yours make combinations or permutations?

here is one i made (combinations) - http://dpaste.com/1315241/
search for powerset for other examples