Compare two string and remove common letters

This is a discussion on Compare two string and remove common letters within the C Programming forums, part of the General Programming Boards category; Helo Cprogramming members, I am new to programming. I started lessons at c in my university and i am having ...

  1. #1
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    Compare two string and remove common letters

    Helo Cprogramming members,

    I am new to programming. I started lessons at c in my university and i am having trouble with an exercise.
    Ok here is what exercise asks for:
    "Write a program that aids with appropriate messages on the screen to read two character strings str1 and str2 even which will be given from the keyboard and then delete all the letters in the variable str1, which appear in the variable str2. The display shows the final result for checking the correct operation of the program."

    For example:
    string1: eleos
    string2: lo
    final result: e e s

    Here is what i have done, but its not working properly..

    Note that i can use only that libraries.


    Code:
    #include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    
    int main()
    {
    char str1[80], str2[80];
    int megethos1, megethos2,max,i,j;
        printf ("Give first string: ");
        scanf ("%s", &str1);
        printf ("Give second string: ");
        scanf ("%s", &str2);
    
        size1= strlen(str1);
        size2= strlen(str2);
    
        for (j=0; j<size2; j++){
               for (i=0; i<size1; i++){
                      if (str1[i]==str2[j])
                          str1[i]=' ';
              }
        }
        printf ("%s", str1);
    
        system("pause");
    
    }
    Thanks in advance

  2. #2
    and the hat of int overfl Salem's Avatar
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    What do you mean "Isn't working"?

    It doesn't compile as posted - is that it?
    Code:
    $ gcc -Wall bar.c
    bar.c: In function ‘main’:
    bar.c:10: warning: format ‘%s’ expects type ‘char *’, but argument 2 has type ‘char (*)[80]’
    bar.c:12: warning: format ‘%s’ expects type ‘char *’, but argument 2 has type ‘char (*)[80]’
    bar.c:14: error: ‘size1’ undeclared (first use in this function)
    bar.c:14: error: (Each undeclared identifier is reported only once
    bar.c:14: error: for each function it appears in.)
    bar.c:15: error: ‘size2’ undeclared (first use in this function)
    bar.c:8: warning: unused variable ‘max’
    bar.c:8: warning: unused variable ‘megethos2’
    bar.c:8: warning: unused variable ‘megethos1’
    Fixing the size declaration problem, it "works" for me, albeit with some warnings which you should fix.
    Code:
    $ gcc -Wall bar.c
    bar.c: In function ‘main’:
    bar.c:10: warning: format ‘%s’ expects type ‘char *’, but argument 2 has type ‘char (*)[80]’
    bar.c:12: warning: format ‘%s’ expects type ‘char *’, but argument 2 has type ‘char (*)[80]’
    bar.c:8: warning: unused variable ‘max’
    bar.c:8: warning: unused variable ‘megethos2’
    bar.c:8: warning: unused variable ‘megethos1’
    bar.c:27: warning: control reaches end of non-void function
    $ ./a.out 
    Give first string: hello
    Give second string: lo
    he   $
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  3. #3
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    You are right abou some errors.. here i fixed them but the programm doesn't do what i wanted to do :P

    Code:
    #include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    
    int main()
    {
    char str1[80], str2[80];
    int size1, size2,i,j;
        printf ("Give first string: ");
        scanf ("%s", &str1);
        printf ("Give second string: ");
        scanf ("%s", &str2);
    
        size1= strlen(str1);
        size2= strlen(str2);
    
        for (j=0; j<size2; j++){
               for (i=0; i<size1; i++){
                      if (str1[i]==str2[j])
                          str1[i]=' ';
              }
        }
        printf ("%s", str1);
    
        system("pause");
    
    }
    Last edited by NiLe; 06-02-2012 at 02:08 PM.

  4. #4
    C++ Witch laserlight's Avatar
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    This is wrong:
    Code:
    scanf ("%s", &str1);
    it should be:
    Code:
    scanf ("%s", str1);
    or better yet:
    Code:
    scanf("%79s", str1);
    Likewise for str2. Your compiler should have warned you about this, so compile at a higher warning level if it didn't.
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  5. #5
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    thank you very much laserlight!!

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