Problem 023

[Tommy137]

See: viewtopic.php?f=50&t=1356

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[iamhigh]

noted!

[iamhigh]

Need your help one more time folks!

Brute forced and arrived at the solution after 3 mins. Checked the forum for this code which runs way faster! but it is confusing the hell out of me. Can somebody type a few insightful words about this?

I am unsure of the code posting rules for this forum - so i am providing a link here to the problem thread page --> edit. I am referring to the one from JavaManIssa - especially around the expressable array that it uses.

Thanks

[hk]

Please no discussion here.
PM me what you don't understand in that solution.

[yashkochar]

I guess this statement needs to be rephrased

A number whose proper divisors are less than the number is called deficient and a number whose proper divisors exceed the number is called abundant.

[Georg]

I guess this statement needs to be rephrased

A number whose proper divisors are less than the number is called deficient and a number whose proper divisors exceed the number is called abundant.

This means:
A number whose sum of its proper divisors is less than the number is called deficient and a number whose sum of its proper divisors exceeds the number is called abundant.
Update:
Corrected. Thank you hk.

[hk]

I guess this statement needs to be rephrased

A number whose proper divisors are less than the number is called deficient and a number whose proper divisors exceed the number is called abundant.

This means:
A number whose sum of its proper divisors are less than the number is called deficient and a number whose sum of its proper divisors exceed the number is called abundant.

Sum is singular so are-->is and exceed-->exceeds

[daniel.is.fischer]

Reads awkwardly. Wouldn't it be better to write "A number for which the sum of its proper divisors ...", as in the first sentence about perfect numbers?
Or "A number n is called deficient if the sum of its proper divisors is less than n and it is called abundant if the sum exceeds n."?

[hk]

Reads awkwardly. Wouldn't it be better to write "A number for which the sum of its proper divisors ...", as in the first sentence about perfect numbers?
Or "A number n is called deficient if the sum of its proper divisors is less than n and it is called abundant if the sum exceeds n."?

I prefer:
"A number n is called deficient if the sum of its proper divisors is less than n and it is called abundant if the sum exceeds n."

Perhaps even better:
"A number n is called deficient if the sum of its proper divisors is less than n and it is called abundant if this sum exceeds n."

[daniel.is.fischer]

Yes, that's better. Who's going to change the problem wording?

Edit: I already did.

[Zifix]

Hi,
I'm struggling to solve this problem. Can somebody please confirm the following stats?
Min Abundant: 12
Max Abundant: 28122
Abundant Cnt: 6965
Min Target: 1
Max Target: 20161
Target Cnt: 1447

As far as I can see they fit the data given posted previously in this thread (20161 being the highest relevant number and 6965 abundant numbers in the range). Are the other ones also OK?
Thanks in advance
Zifix

[spade78]

I just solved this one. All the stats are correct except for:
Target Cnt: 1456

[yotama9]

Hi guys.

I'm trying to solve this problem and I can't get the right solution. Is there some milestone results to check my code? (for example, the sum of all the numbers below 1000 which are not the sum of to abundant numbers) This will be very useful for debugging

Thanks.

[thundre]

There are 21 abundant numbers below 100.

The sum of the numbers below 100 that cannot be expressed as the sum of two of these is 2766.

That should help your debugging.

[CMinus]

the smallest number that can be written as the sum of two abundant numbers is 24

In fact the first two abundant numbers are 12 , 18 So their sum = 30 !!
Am I right or I have misunderstanding ??

[branduren]

Just a little misunderstanding.
12 + 12 = 24
but I guess 30 is the second smallest.

[rayfil]

@CMinus

Your post has been merged with the proper thread related to Problem 23.

We realize you are new to this forum. Please read the sticky thread entitled "Comments, questions and clarifications about PE problems". By using the suggested search procedure, you will find that most (if not all) of the older problems already have a thread started for them. And, in many cases, your
inquiry may already have been covered.

[CMinus]

@rayfill I am sorry but , I searched the forum & I didn't find the post !!

[Artemiye]

Can someone take a look at my code? It's in C++ - I get an answer that's very close (within ~1000), but obviously not the correct answer.

[nebffa]

Hi - I just completed problem 023. In my humble opinion, I firmly believe the wording of this question should be changed from

Find the sum of all the positive integers which cannot be written as the sum of two abundant numbers.

to

Find the sum of all the positive integers which cannot be written as the sum of two abundant numbers (the two abundant numbers are allowed to be the same).

I spent some time thinking what was wrong with my code until I realised perhaps the question was ambiguous. Surely enough on changing my "i + 1" to "i" in one of my loops I got the correct answer.


Thankyou for your consideration,

Ben