🔒 help with code

[plush marsh]

pls give me hints of where im going wrong in my logic

[lucid iris]

@plush marsh

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[plush marsh]

def largest_cube(n):
    '''
    Assume n is an integer > 1.
    Return the largest value of k such that k**3 is strictly
    less than n. For example, if n is 30, the answer would be
    3, since 3**3 = 27, which is the largest perfect cube 
    less than 30.
    '''
    number = 0
    for i in range(n):
        while n**3 < n:
            if n**3 < n:
                number += n

    return number
print(largest_cube(30))  

^same code in photo

[acoustic onyx]

I don't think you'll need a for loop and a while loop here

[plush marsh]

but shouldnt this work also

[acoustic onyx]

No, it doesn't quite make sense what you're doing with this code

all you need to do is increase number, check it's cube, and stop when the cube is greater than n

so if the number is 30 like in the example

we would check
1 ** 3
2 ** 3
3 ** 3

4 ** 3 is greater than 30, so the loop would stop

[acoustic onyx]

I would use a while loop here instead of a for loop

if you do for num in range(n)

that's going to give you 0, 1, 2, 3, 4, 5....30

you don't need to check all 30 numbers

you only need to check numbers whose cube is smaller than 30

[acoustic onyx]

be careful with the difference of = and ==

[plush marsh]

oh it works

[acoustic onyx]

and why do you think you need num and number? How are they different?

Just because it works for one example, doesn't mean you got it correct

run more tests

[plush marsh]

yea nvm

[acoustic onyx]

You're overthinking it a bit

Your while loop condition is good

except is should be <= instead of <

Oh nevermind it says less than n

< is correct

[plush marsh]

idk how to increment num in a while loop

[acoustic onyx]

def largest_cube(n):
    number = 1
    while number ** 3 <= n:
        number += 1

Look at this logic here

This logic will check 1 ** 3 to see if it is below 30 (if n is 30)

if it's still less than 30, then it will check 2 ** 3

if it's still less than 30, it will check 3 ** 3

do you see how this is working?

[plush marsh]

yea

[acoustic onyx]

We're going to keep increasing number by 1 until number ** 3 is greater than (or equal to) n

[plush marsh]

much simpler

[acoustic onyx]

There's one slight flaw though

What do you think it might be?

[plush marsh]

hmm

i think if i test 3 it doesnt work

actually idk

[acoustic onyx]

The issue is that number has to go one too far to figure out when the cube is too large

when n is 30, number will be 4 after the loop, because when testing 4 ** 3, we can see that 64 is larger than 30

So for this, we want to return 3, not 4

[plush marsh]

would subtracting 1 help?

[acoustic onyx]

exactly 🙂

[plush marsh]

!close

[lucid iris]

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