(Aug 19, 2016 06:05 AM)Minimalist Wrote:  Shit, I hate to bump 3 year old threads but I found these challenges to be helpful with exercising my critical thinking and mathematical skills. Nice share.

(Aug 19, 2016 03:31 PM)Himmayn Wrote:  Thanks! :D

Didnt know how much slower if statements make your code, noticed it on one of the challenges.

problem: 2520 is the smallest number that can be divided by each of the numbers from 1 to 10 without any remainder.
What is the smallest positive number that is evenly divisible by all of the numbers from 1 to 20?

i did it first like this

Code

#include "Includes.h"

int smallNumber = 20;
int divider = 1;

int main()
{
    while (true)
    {
        if (smallNumber % divider != 0)
        {
            smallNumber += 20;
            divider = NULL;
        }
        if (divider <= 20)
        {
            divider++;
        }
        else if (divider == 20)
        {
            cout << "smallest positive number that is evenly divisible by all of the numbers from 1 to 20: " << smallNumber << endl;
            break;
        }
        
    }
}

it takes forever to get to the right number.

but if you do it like this

Code

int i = 20;

while (i %  2 != 0 || i %  3 != 0 || i %  4 != 0 || i %  5 != 0 ||
         i %  6 != 0 || i %  7 != 0 || i %  8 != 0 || i %  9 != 0 ||
         i % 10 != 0 || i % 11 != 0 || i % 12 != 0 || i % 13 != 0 ||
         i % 14 != 0 || i % 15 != 0 || i % 16 != 0 || i % 17 != 0 ||
         i % 18 != 0 || i % 19 != 0 || i % 20 != 0) {
    i += 20;
}

it takes less than a second lol

(Aug 19, 2016 04:48 PM)MeshCollider Wrote:  It's not the if statements that are slow, it's the fact that you are looping may more times in the first code that in the second. The second code is not particularly elegant though, and isn't easily modified to other numbers. The problem is really just looking for the lowest common multiple of all the numbers.
But nice work, good to see some more members taking interest :)

(Aug 20, 2016 03:30 PM)Steve Miller Wrote:  Wow, finally one interesting thread.

I've been practicing on www.hackerrank.com in my spare time. They have thousands of challenges. Usually the easy ones are extremely hard.

I would recommend you guys check it out and see how it works.

You earn Hackos by solving challenges. And each code submitted has up to 20 test cases. If you cannot figure out which one is failing and why, you can buy that test case using your earned Hackos and see why it's failing.

Various topics and they just keep adding and adding stuff and have so many languages to choose from.