CODEWITHSUNDEEP
c
Berke Cagkan Toptas
Berke Cagkan Toptas

Reputation: 1034

Long data type calculation in C

I have a simple program that finds automorphic numbers up to given number. The problem is it just finds the number which square parameter is bound of int.

for example : 90625 x 90625 = 8212890625 but program could't find it.

Question : What is the problem with long type here? It act like int. Is there a cast to int for the square parameter anywhere of the code?

#include <stdio.h>
int main(void)
{
   int n;
   long i;

   printf ("Enter a value:\n") ;
   scanf ("%d",&n) ;
   printf ("Automorphic numbers:\n") ;
   for (i=1L ; i<=n ; i = i+1L)
   {
       long square = i*i ;

       if (square % 10L == i || square % 100L == i || square % 1000L == i || square % 10000L == i || square % 100000L == i || square % 1000000L == i || square % 10000000L == i)
       printf ("%li\n", i) ;
   }
}

Upvotes: 0

Views: 1565

Answers (2)

Bruno Costa
Bruno Costa

Reputation: 334

For 64 bits you shall use long long.

EDIT: long corresponds to long int which can have the same size as int. You can use sizeof to check the size taken.

Upvotes: 1

ensc
ensc

Reputation: 6994

C guarantees the following limits (n869 C99 draft):

-- minimum value for an object of type int
    INT_MIN                     -32767 // -(215-1)

-- maximum value for an object of type int
    INT_MAX                     +32767 // 215-1

-- maximum value for an object of type unsigned int
    UINT_MAX                     65535 // 216-1

-- minimum value for an object of type long int
    LONG_MIN               -2147483647 // -(231-1)

-- maximum value for an object of type long int
    LONG_MAX               +2147483647 // 231-1

-- maximum value for an object of type unsigned long int
    ULONG_MAX               4294967295 // 232-1

-- minimum value for an object of type long long int
    LLONG_MIN     -9223372036854775807 // -(263-1)

-- maximum value for an object of type long long int
    LLONG_MAX     +9223372036854775807 // 263-1

[5.2.4.2.1  Sizes of integer types <limits.h>]

When you need defined sizes, use uint64_t and similar datatypes.

Upvotes: 5

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