[Tutor] Root and power

[Job Hernandez]

How is it going tutors?

The following problem seems impossible to me:

"*Write a program that asks the user to enter an integer and prints two
integers, root and pwr, such that 0 < pwr < 6 and root^pwr (root**pwr) is
equal to the integer entered by the user. If no such pair of integers
exists, it should print a message to that effect*."

I would like to solve this problem myself so please don't give me the
solution.

I need to learn how in the world do find the root and power of an integer
that x user entered? I haven been looking on the python website for an
appropriate function but I have not.

If you have the time can you please tell me about the functions and other
facts I need to know in order to solve this problem?

Is there a book you guys recommend for total beginners who have no ideal of
what computer science and programming is?

Thank you,

Job
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[Alan Gauld]

Post by Job Hernandez
How is it going tutors?

I made a reply in the thread 'Abs' started on July 27th.

Basically you can use the pow() function.

The power lies between 1-5.
The largest root will be the same as the user input
since X**1 = X. So you always have at least 1 answer!

You need to iterate up to the power of 1 solution to
find if there is a smaller pair of integers.
Some may have several, for example 16 yields:

16**1
4**2
2**4

Your assignment doesn't make it clear how that should be handled...
--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
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[David Palao]

Post by Job Hernandez
How is it going tutors?
"*Write a program that asks the user to enter an integer and prints two
integers, root and pwr, such that 0 < pwr < 6 and root^pwr (root**pwr) is
equal to the integer entered by the user. If no such pair of integers
exists, it should print a message to that effect*."
I would like to solve this problem myself so please don't give me the
solution.
I need to learn how in the world do find the root and power of an integer
that x user entered? I haven been looking on the python website for an
appropriate function but I have not.
If you have the time can you please tell me about the functions and other
facts I need to know in order to solve this problem?
Is there a book you guys recommend for total beginners who have no ideal of
what computer science and programming is?
Thank you,
Job
_______________________________________________
https://mail.python.org/mailman/listinfo/tutor

Hello,
First, you need an algorithm that solves your problem. Once you have
it, you need to implement it in Python.
For the algorithm. Although there are theorems and all sort of smart
mathematical tricks you could use, given the conditions you have, have
you considered to use a brute force approach? I mean: if all involved
numbers are positive you could start testing different values for root
from 0 on, and for each value test pwr from 1 to 5 until you find
either a solution, something bigger than x.
Once you chose the algorithm, for the actual implementation you have
to say what part you are blocked at.
Best.
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[Steven D'Aprano]

On Tue, Jul 28, 2015 at 08:29:00PM -0700, Job Hernandez wrote:
[...]

Post by Job Hernandez
I need to learn how in the world do find the root and power of an integer
that x user entered? I haven been looking on the python website for an
appropriate function but I have not.

Let's suppose the user entered 36. Then the possible answers are:

36**1 = 36
6**2 = 36

and I think that's about it. We know that pwr=0 won't give any solutions
unless the number itself is 1:

1**0 = 1
2**0 = 1
3**0 = 1
4**0 = 1

etc. So if the user enters 1, you can just print root=1 and pwr=0 and
you are done. (For that matter, you could print any value for root!)

Otherwise, for any pwr other than 1, we want to find some root such
that:

root**pwr = the number the user entered

How might we do this for, say, pwr=2, and the number 25? There's no
built in function for this, instead you need to do a loop, testing each
number in turn:

1**2 = 1, too small
2**2 = 4, too small
3**2 = 9, too small
4**2 = 16, too small
5**2 = 25, equals the user's number

so this tells us that 25 is a perfect square, and we can now print
root=5, pwr=2.

How about pwr=2, number = 27?

1**2 = 1, too small
2**2 = 4, too small
3**2 = 9, too small
4**2 = 16, too small
5**2 = 25, too small
6**2 = 36, too big

So this tells us that 27 is NOT a perfect square. Let's check to see if
it's a perfect cube:

1**3 = 1, too small
2**3 = 8, too small
3**3 = 27, equals the user's number

so 27 is a perfect cube, and we can print root=3, pwr=3.

Obviously we don't actually need to check root=1, since 1 to the power
of anything is always 1. Let's try (say) 59:

2**2 = 4, too small
3**2 = 9, too small
...
7**2 = 49, too small
8**2 = 64, too big -- pwr cannot be 2
2**3 = 8, too small
3**3 = 27, too small
4**3 = 64, too big -- pwr cannot be 3
2**4 = 16, too small
3**4 = 81, too big -- pwr cannot be 4
2**5 = 32, too small
3**5 = 243, too big -- pwr cannot be 5
2**6 = 64, too big -- pwr cannot be 6

At this point you have a choice:

print "No such root and pwr"

print "root=59, pwr=1"

but I guess the second one is probably going against the spirit of the
question. Or maybe not? Hard to say.


Obviously you shouldn't write out all the tests by hand:

# No, don't do this!
if 2**2 == number:
print("root=2, pwr=2")
elif 3**2 == number:
print("root=3, pwr=2")
elif 4**2 == number:
print("you've got to be kidding, I quit!")


Instead you will use for-loops and range, and break to exit out of the
loop early.

for pwr in range(2, 7):
for root in range(2, num):
...


Is that enough of a hint, or do you need more assistence?

[Job Hernandez]

Thank you all,\.
Programming is the hardest thing i have ever tried to learn.

So thank you for your help.

Job

Post by Job Hernandez
How is it going tutors?
"*Write a program that asks the user to enter an integer and prints two
integers, root and pwr, such that 0 < pwr < 6 and root^pwr (root**pwr) is
equal to the integer entered by the user. If no such pair of integers
exists, it should print a message to that effect*."
I would like to solve this problem myself so please don't give me the
solution.
I need to learn how in the world do find the root and power of an integer
that x user entered? I haven been looking on the python website for an
appropriate function but I have not.
If you have the time can you please tell me about the functions and other
facts I need to know in order to solve this problem?
Is there a book you guys recommend for total beginners who have no ideal
of what computer science and programming is?
Thank you,
Job

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