Re: Find the sum of all the prime numbers
 

There is other method also which does not require sqrt.

Re: Find the sum of all the prime numbers
 

Interesting, so we will find the factor of n within any of the number in sqrt(n) if not then its a prime number.

Re: Find the sum of all the prime numbers
 

let me tell you the logic now
it is very simple
look if k is any no.
then k can be represented as k=i*j
where i and are k's factor
now i varies from 1to k
and j varies from k to 1
but for prime no. we check for i=2 to k/2
acordingly j will varies from (k/2) to 2
now if 2 is a factor of k
then automatically k/2 is also a factor and so on
that is when i increases, j decreases
so we continue like this then there is condition that both i and j becomes equal
so i*i=k
so i=sqrt(k)
but if k is not a square of any no. then i increases upto a integer just less than sqrt iof k
thats all what i did
now try this problem
for a given no. print all its prime factors that is
if input is 12 out put should be 2*2*3
using the hint that the lowest factor of any no. other than one is always prime
try it

Re: Find the sum of all the prime numbers
 

friendsforniraj thats a good logic explained.

Re: Find the sum of all the prime numbers
 

thank u sir
but ma name is niraj

Re: Find the sum of all the prime numbers
 

I will try putting that from now on.

Re: Find the sum of all the prime numbers
 

why do we need a square root

Re: Find the sum of all the prime numbers
 

Excellent explaination. Now any one can understand either he is new or experience

Re: Find the sum of all the prime numbers
 

for(j=2;j<=sqrt(i);j++) :cryin:

is similar to

for(j=2;j*j <= i;j++) :p

so, no sqrt in here since it is really slow. At least if was some years ago.

Re: Find the sum of all the prime numbers
 

for getting the prime number try

http://en.wikipedia.org/wiki/Sieve_of_Eratosthenes

No devisions in here