[Tutor] Beginner's question

[Walter Prins]

Hi Peter,


On 22 November 2012 12:55, Peter O'Doherty <mail at peterodoherty.net> wrote:

> Hi list,
> Firstly, apologies for the low-level nature of this question - it's really
> quite basic but I don't seem to be able to solve it.
>
> I need to write a program that examines 3 variables x, y, z, and prints
> the largest odd number. I've tried all sorts of variations and this is the
> current version:
>
> x, y, z = 26, 15, 20
>
> if x > y and x > z and x%2 != 0:
>     print 'x is largest and odd'
> elif y > x and y > z and y%2 != 0:
>     print 'y is largest and odd'
> elif z > x and z > y and z%2 != 0:
>     print 'z is largest and odd'
> else:
>     print 'no odd'
>

The key logical mistake you make is that by your current logic the
*smallest* number can never be the largest odd number, which is obviously
false as in your example.

Break the problem down (divide and conquer).  Suppose I gave you only 2
numbers, and you had to say which of the 2 numbers were the largest odd,
what would be the possible outcomes and what would the the solution be?
(Hint, both can be odd, only x can be odd, only y can be odd, or neither
can be odd.)   Once you have that answer, then repeat the exact same
solution for the first 2 numbers and apply to the answer from x&y and and
the remaining z.  The result from that is tells you the largest odd number
from all 3. (Aside, your question states to print the largest odd number,
which I interpret to mean the value, not the name of the variable holding
the value.  )

Walter
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