[Tutor] Algorithm

[Alan Gauld]

On 28/12/15 12:34, cicy felix wrote:

>   Create a function get_algorithm_result to implement the algorithm below
> Get a list of numbers L1, L2, L3....LN as argument
> Assume L1 is the largest,  Largest = L1
> Take next number Li from the list and do the following
> If Largest is less than Li
>    Largest = Li
>  If Li is last number from  the list then
>   return Largest and come out
>  Else repeat same process starting from step 3

OK, That seems fairly clear. Although it does
seem to imply a while loop which is maybe not
the best option here.(see below)

> This what I've come up with:

Thanks for showing us the code, but there are several
issues with it

> def get_algorithm_result( numlist ):
>  largest = numlist[0]
>  i = 1
>  while ( i < len(numlist) ):
>    if ( largest < numlist[i]):
>      largest = numlist[i]
>      i = i + 1

Notice that you only increase i if the if test is true.
If largest >= numlist[i] then your loop will simply go
round and round forever. The normal way in Python to
process all elements in a list is to use a for loop.

In your case that would look an awful lot simpler.
Try it.

>      return largest
>      numlist1 = [1,2,3,4,5]
>      numlist2 = [10,20,30,40,50]

I've no idea what you think these numbers are for,
they are not mentioned in your problem description.

>      largest = get_algorithm_result(numlist1)

This should(if it worked properly) return 5

>      print largest

So this (should) always print 5

>      largest = get_algorithm_result(numlist2)

and his should(if it worked properly) return 50

>      print largest

and this should print 50.

Two largests - isn't that a bit confusing?
Especially since neither number may be in your
original list of numbers.

> And I keep getting this error :
>   .  test_maximum_number_two
> Failure in line 15, in test_maximum_number_two    self.assertEqual(result,
> "zoo", msg="Incorrect number") AssertionError: Incorrect number
> Using unittest


Since you don't show us any code involving test_maximum_number_two
or even maximum_number_two() we can't help you there.

But it does seem to me that you are over complicating things.
Even if you stick with a while loop, just follow the algorithm
you were given and it should work.

One final point. You are printing the results but your problem states
that you should write a function that *returns* the largest. Not one
that prints it.

In general this is what functions should always do - return
values not print them. It makes them much more reusable and flexible.
You can always print the output later using:

print get_algorithm_result(numlist)


-- 
Alan G
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