On 29/10/2013 10:18, Walter Prins wrote:
Hi,
On 28 October 2013 20:55, Alex Tenno <alex.te...@gmail.com
<mailto:alex.te...@gmail.com>> wrote:
Hey everyone,
I'm encountering a problem with a python function that I am supposed
to create.
OK. You should try to actually write the function yourself first, then
give concrete details about what you've tried, and how you're stuck.
I want my function to look at a string, and then replace each letter
in the string with its relative position in the alphabet. for
example, 'abcde' would return '12345', 'zabd' would return '4123',
and 'xpft' would return '4213'.
Is this the exact problem statement or are you paraphrasing? I'd like
to make sure I understand the question.
I have been given hints that tell me "You may want to iterate over
the letters ch in s as in the for loop above, and inside that for
loop, count the number of letters that are in s and come before the
loop variable ch. You will also need an accumulator to build the
permutation the function will return." any help would be greatly
appreciated.
OK so you've been given some high level idea of what to do. Try to break
this down to more concrete steps, perhaps firstly still only pseudocode,
and eventually translate that to Python.
The idea embodied in the suggestion is based on the observation that you
can determine the relative position in the alphabet, of each character
in the word by, looking the letter in the word, and then counting how
many /distinct/ letters in the word are smaller than or equal to the
letter under scrutiny. For the smallest letter, this will by definition
only count the letter itself (if you compare with every distinct letter
in the word), resulting in a count of 1. For the second smallest
letter, this will therefore result in the smallest letter and the 2nd
smallest letter being counted, resulting in a count of 2. And so on.
These counts then give the relative position of each letter in the
alphabet. Amit's suggestion boils down to the same idea -- sort the set
of distinct letters in the string, and then look up the relative
position of each letter in your original string in this sorted set.
Next questions to think about: How do you calculate the set of distinct
letters in the string? (Hint: Look at set() function.) How do you
calculate the count of smaller letters from this distinct set? (Hint:
Loop over the set and count as you go.) Or convert this set to a sorted
list to then lookup against. (Hint: Look at the list() function and the
sorted() function.)
Walter
An extremely strong hint for all newbies is to try any and all of the
above suggestions at the interactive prompt. This tool is one of
Python's great strengths so use it.
--
Python is the second best programming language in the world.
But the best has yet to be invented. Christian Tismer
Mark Lawrence
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