How to Compare elements in arrays

This is a discussion on How to Compare elements in arrays within the C Programming forums, part of the General Programming Boards category; Code: I need some help in finding elements in array "aqq" that matchs with those in "arr" My code just ...

  1. #1
    axe
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    How to Compare elements in arrays

    Code:
     I need some help in  finding elements in array "aqq" that matchs with those in "arr"
    My code just prints found as zero 
    
       for(i=0;i<count;i++)
       {
         found=0;
         for(j=0;j<k;j++)
         {
           if(strcmp(arr[j],aqq[i])==0)
           {
             found++;
           }
         }
         printf("%s",found);
       }

  2. #2
    Aia
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    strcmp works only with strings and not individual elements of a string.
    Assuming that arr[j]and aqq[i] are 2D arrays and not elements of a string.
    Take the found=0; outside of the first for loop.
    printf("&#37;s",found); /* Isn't found an int. Change to %d */
    Last edited by Aia; 11-14-2007 at 03:51 PM.

  3. #3
    axe
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    Code:
    But i need to reset found to =0 but i am comparing using more that one string
    
    say aqq has {and, go, to, the, nowhere}
          arr has {it, to, and, and, and, on, to, the, and, go, go, go}

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    It should work if you change the printf() format specifier to &#37;d (assuming found is an int).

  5. #5
    Aia
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    Quote Originally Posted by axe View Post
    Code:
    But i need to reset found to =0 but i am comparing using more that one string
    
    say aqq has {and, go, to, the, nowhere}
          arr has {it, to, and, and, and, on, to, the, and, go, go, go}
    Code:
    #include <stdio.h>
    #include <string.h>
    
    int main ( void )
    {
        char aqq[][8]= { "and", "go", "to", "the", "nowhere"};
        char arr[][4] = {"it", "to", "and", "and", "and", "on", "to", "the", "and", "go", "go", "go"};
        int i, j;
        int first_array = sizeof aqq / sizeof aqq[0];
        int second_array = sizeof arr / sizeof arr[0];
        int results[sizeof aqq / sizeof aqq[0]] = { 0 };
        
        for ( i = 0; i < first_array; i++)
        {
         	for ( j = 0; j < second_array; j++ )
         	{
           		if ( strcmp(arr[j], aqq[i]) == 0 )
           		{
             		++results[i];
           		}
        	}
        	printf( "&#37;s repeats %d times\n", aqq[i], results[i] );
        }
        getchar();    
        return 0;
    }
    Last edited by Aia; 11-14-2007 at 04:26 PM.

  6. #6
    axe
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    wow!! sweet!! thanks!!

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    Would you please explain me the code?

  8. #8
    Aia
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    Quote Originally Posted by eXeCuTeR View Post
    Would you please explain me the code?
    What part do you not understand?

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    Basically, the more complicated part:
    Code:
        int first_array = sizeof aqq / sizeof aqq[0];
        int second_array = sizeof arr / sizeof arr[0];
        int results[sizeof aqq / sizeof aqq[0]] = { 0 };
        
        for ( i = 0; i < first_array; i++)
        {
         	for ( j = 0; j < second_array; j++ )
         	{
           		if ( strcmp(arr[j], aqq[i]) == 0 )
           		{
             		++results[i];
           		}
        	}

  10. #10
    CSharpener vart's Avatar
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    sizeof aqq / sizeof aqq[0] - calculates number of elements inthe array

    for ( i = 0; i < first_array; i++) - loops through all elements in the array

    strcmp(arr[j], aqq[i]) - compares current string in one array to string in another array

    ++results[i] - if strings are equall - increases the counter

    So what part exactly is hard to understand?
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

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    Code:
    strcmp(arr[j], aqq[i]) == 0
    equals to 0? why?

    and what does
    Code:
    results[sizeof aqq / sizeof aqq[0]] = { 0 };
    do?

    thanks so much.

  12. #12
    Registered User hk_mp5kpdw's Avatar
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    Quote Originally Posted by eXeCuTeR View Post
    Code:
    strcmp(arr[j], aqq[i]) == 0
    equals to 0? why?
    It's not saying it equals 0, it is part of an "if" statement and is saying "if it is equal to 0", not "it is equal to 0". The strcmp function returns 0 if the two strings are equal so the whole "if" statement effectively says "if the two strings are equal to each other".

    and what does
    Code:
    results[sizeof aqq / sizeof aqq[0]] = { 0 };
    do?

    thanks so much.
    It was already explained what sizeof aqq / sizeof aqq[0] does. So, combining it with the declaration of the integer array we can say that it creates an integer array of 8 elements (the same number of character pointer elements as aqq contains) called results. It also initializes all the values in that array to 0.
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  13. #13
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    Yeah, I meant that why if it's TRUE it will equal to 0.

    Thought it would return 0 if 2 strings are equal at first, guess I was right.

    Thanks mate!

  14. #14
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    The reason strcmp() returns 0 for "equal" is that it essentially returns "the a signed difference" - this means that strcmp() can ALSO tell you which if the strings is the greater if they are different. If the return value is > 0, the first string is "greater". If the return value is < 0, the second string is the greater.

    So, strcmp("abcd", "abcc") returns something greater than zero, swap the strings around, and you get a negative return. Note that it's not guaranteed what the VALUE itself is, it may be 1 and -1 for all strings, or it may be (commonly is) the difference between the first different letters in the string.

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