Thread: whether number is prime or not

If the number is greater than 2^32(4294967296)then how to determine whether is it prime or not? Ex:Is 4437864713 a prime number ?

Use long long or __int64.

@Salem : I know the algo of the problem but main problem is how to handle the large number.As we can't use double data type cause we need to use % operator.

Can any provide me a little code snippet for handling large number(>4294967296) and we can use % operator too with the number.

Code:

unsigned long long number = 0x7FFFFFFFFFFFFFFF;

printf("%lld\n", number);

Originally Posted by amite

@Salem : I know the algo of the problem but main problem is how to handle the large number.As we can't use double data type cause we need to use % operator.

Can any provide me a little code snippet for handling large number(>4294967296) and we can use % operator too with the number.

Unless your compiler is an antique, it has a 64 bit integer type.

Check your docs... Different comiplers implement 64 bit integers in different ways.
It might be one of...

1) unsigned long long int
2) #include <stdint.h> then use uint64_t
3) unsigned long int

The easiest way to tell is to try different combinations and use sizeof() ... a 64 bit int will return 8 instead of 4.

Originally Posted by Fader_Berg

Code:

unsigned long long number = 0x7FFFFFFFFFFFFFFF;

printf("%lld\n", number);

the number i have is 600851475143.

unsigned long long number=600851475143;

Even this satement give error.When i use 600851475 then it give the result.

Originally Posted by Fader_Berg

Code:

unsigned long long number = 0x7FFFFFFFFFFFFFFF;

printf("%lld\n", number);

the number i have is 600851475143.

unsigned long long number=600851475143;

Even this satement give error.When i use 600851475 then it give the result.I am using codeblock on windows.

Try...

Code:

#include <stdio.h>
#include <stdint.h>

int main (void)
 { uint64_t x;

    x = 600851475143; 

    printf("%lld", x );
    
    return 0;
     }

Originally Posted by Fader_Berg

Code:

unsigned long long number = 0x7FFFFFFFFFFFFFFF;

printf("%lld\n", number);

Originally Posted by CommonTater

Try...

Code:

#include <stdio.h>
#include <stdint.h>

int main (void)
 { uint64_t x;

    x = 600851475143; 

    printf("%lld", x );
    
    return 0;
     }

I tried the following on windows(codeblock) and linux(gcc) :

Code:

#include <stdio.h>
#include <stdint.h>
int main()
{
        uint64_t x;
        unsigned long long y;
        unsigned long int z;
        printf("%d\n",sizeof(x));
        printf("%d\n",sizeof(y));
        printf("%d\n",sizeof(z));
        return 0;
}

Results in both case are same :
8
8
4

but when i try to assign value 600851475143 to x or y then i get compile time error as :

error : integer constant is too large for "long" type

that's my problem when why compiler show such error while the number is too short than 2^64.
One more thing long is expected to have size of 8 byte but here we get 4 byte ,why?

Originally Posted by amite

I tried the following on windows(codeblock) and linux(gcc) :

Code:

#include <stdio.h>
#include <stdint.h>
int main()
{
        uint64_t x;
        unsigned long long y;
        unsigned long int z;
        printf("%d\n",sizeof(x));
        printf("%d\n",sizeof(y));
        printf("%d\n",sizeof(z));
        return 0;
}

Results in both case are same :
8
8
4

but when i try to assign value 600851475143 to x or y then i get compile time error as :


that's my problem when why compiler show such error while the number is too short than 2^64.
One more thing long is expected to have size of 8 byte but here we get 4 byte ,why?

long is generally only 32 bits... you need long long to get 64.

That doesn't make any sense... your number is only 39bits... there's no reason it won't fit in a uint64_t ... unless your compiler is all messed up... Did you try this both on Windows and Linux?

It works here on both VC++ (with my re-worked header file) and on PellesC ....