Want to protect your cyber security and still get fast solutions? Ask a secure question today.Go Premium

x
  • Status: Solved
  • Priority: Medium
  • Security: Public
  • Views: 331
  • Last Modified:

how to compare integers in an array

Lets say I have 2 arrays:
----------------------------------------
int* a=new int[9]
int* b=new int[9]

a=[1,2,3,4,5,6,7,8,9]
b=[1,2,3,4,6,4,3,2,1]
----------------------------------------
compare(a,b,first_5) => false

Now.. how can I compare first 5 (or first n) integers, without having to use a while loop (or for)?
Is there a faster way at all (then to use a loop)?
Thank you!

Jurij
0
jurij
Asked:
jurij
1 Solution
 
jkrCommented:
You can use 'memcmp()':

memcmp ( a, b, 5 * sizeof ( int));

This will do a binary compare for the first 5 elements in the arrays, which is equal to compare each of the elements.

Here's a smple from the VC++ docs

Example

/* MEMCMP.C: This program uses memcmp to compare
 * the strings named first and second. If the first
 * 19 bytes of the strings are equal, the program
 * considers the strings to be equal.
 */

#include <string.h>
#include <stdio.h>

void main( void )
{
   char first[]  = "12345678901234567890";
   char second[] = "12345678901234567891";
   int result;

   printf( "Compare '%.19s' to '%.19s':\n", first, second );
   result = memcmp( first, second, 19 );
   if( result < 0 )
      printf( "First is less than second.\n" );
   else if( result == 0 )
      printf( "First is equal to second.\n" );
   else if( result > 0 )
      printf( "First is greater than second.\n" );
   printf( "Compare '%.20s' to '%.20s':\n", first, second );
   result = memcmp( first, second, 20 );
   if( result < 0 )
      printf( "First is less than second.\n" );
   else if( result == 0 )
      printf( "First is equal to second.\n" );
   else if( result > 0 )
      printf( "First is greater than second.\n" );
}


Output

Compare '1234567890123456789' to '1234567890123456789':
First is equal to second.
Compare '12345678901234567890' to '12345678901234567891':
First is less than second.

0
 
GregToombsCommented:
I think the suggested call to memcmp is the fastest route, simply because it has been optimized by previous programmers. Conceptually speaking, keep in mind that any such comparison, including memcmp itself, needs to use a loop of some description.
0

Featured Post

Independent Software Vendors: We Want Your Opinion

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Tackle projects and never again get stuck behind a technical roadblock.
Join Now