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@repstosd great, how do you know a number is prime?
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@noctemx yes and the implementation would be... Point was in order to find prime have to try all numbers... Not just the primes
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@billgates just trying to help in the "how to know if a number is prime" question
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@billgates
You can just save a seive of all primes till 7million. Can be done in less than 1 sec. For even better results, there exist optimized seive of Eratosthenes which uses bitwise operators. Just check your number is not divisible by all primes(approx 7million/ln(7million)).
I spend all morning on trying to solve an Algo problem for upcoming interview practice (Euler #3) that comes down to implementing IsPrime.
I remember reading once how Sieve of Eratosthenes
Isa the right way to go do when I first started I wanted to use that.
Then I couldn't think of the right code though so I went with Brute Force (for all numbers upto X see X is divisible by it)
It actually worked but I wanted to just try the "right way".
It's way slower and actually ended up with the wrong answer...
But at this point I don't give a **** anymore.
I guess lesson learned... Use Brute Force first... Then optimise for a problem more elegant solution.
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