whats wrong with my code?

This is a discussion on whats wrong with my code? within the C Programming forums, part of the General Programming Boards category; hello all..im in need of some assistance with my homework assignment. but before you say "oh no..", please read on. ...

  1. #1
    Unregistered
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    whats wrong with my code?

    hello all..im in need of some assistance with my homework assignment. but before you say "oh no..", please read on. i did make an attempt! but for some reason...it is not working...so im going to post my assignment..and then show you what i came up with..please please please..tell me what im doing wrong..

    Part 1.
    Write a C function that deletes all occurrences of an element from an array starting
    from a given index. The prototype of the function is as follows:

    //Preconditions: The first parameter is an integer array; the
    second parameter is an integer representing the number
    of elements in the array; the third parameter is the
    number that is to be deleted from the array; and the
    fourth parameter is the index from which the search for
    deletion should start.

    //Postconditions: The function deletes all elements
    whose value is equal to item starting from the index
    loc. The size of the array will decrease if one or more
    copies of item existed in the array. Therefore function
    changes the number of elements in the array as well. The
    function also returns the number of deleted items.
    int delete_elemet(int a[], int *n, int item, int loc);

    Part 2.
    Write a program that reads a sequence of unknown number of integers into an
    array. There may be a maximum of 20 integers in the input, so you should define
    the size of the array to be 20. Your program should then remove duplicates of all
    numbers in the array using the function that you wrote in part 1. After deleting the
    duplicates, your program should also print how many copies are deleted for each
    number having duplicates.
    Output Specifications:

    Sample Run 1:
    Enter some integers (maximum of 20):
    10 25 38 25 40 10 10 50 38 25 10
    Value 10 : 3 copies are deleted.
    Value 25 : 2 copies are deleted.
    Value 38 : 1 copy is deleted.
    The resulting array is:
    10 25 38 40 50

    Sample Run 2:
    Enter some integers (maximum of 20):
    21 21 21 21 21 21 21
    Value 21: 6 copies are deleted.
    The resulting array is:
    21

    Requirements:
    In order to get full credits, you must write the function delete_element() as
    described in part 1 and you must call it in your main function appropriately to
    perform the task described in part 2.
    Your main function should call the function delete_element() properly so that
    it can use the value that the function returns to print the number of copies deleted
    from the array. This printing must be done in the main function, not in the function
    delete_element() .


    ok..that was the assignment...and this is what i came up with:

    #include <stdio.h>
    int delete_element(int a[], int *n, int item, int loc);
    int d;
    int main()
    {
    int cnt=0, a[], *n, p, I;
    while(*n<=20) {
    printf(“Enter some integers (maximum of 20): \n”);
    }
    scanf(%d, &a[*n]);
    if(cnt <=*n){
    delete_element(a[], n, cnt + 1, cnt);
    printf(“\n”);
    if(d>1){
    printf(“Value %d: %d copies are deleted.”, *n, d);
    }
    else{
    printf(“Value %d: %d copy is deleted.”, *n, d);
    p=p+d;
    }
    cnt= cnt + 1;
    }
    printf(“The resulting array is: \n”);
    for(I=0; I <=p; I ++){
    printf(“%d”, a[I] );
    }

    int delete_element(int a[], int *n, int item, int loc);
    {
    int x, y, d=0, l;

    for(x=loc; x<n; x=y)
    {
    y=x;
    if(a[x]==item)
    {
    for(l=x; l<n-1; l++) a[l]=a[l+1];
    d++; n--;
    } else y++;
    }
    return d;
    }


    ANY suggestions will be greatly appreciated! Thank you..

  2. #2
    ATH0 quzah's Avatar
    Join Date
    Oct 2001
    Posts
    14,826
    Well this is a fairly obvious one:
    Code:
    int main() 
    { 
       int cnt=0, a[], *n, p, I; 
       while(*n<=20) { 
       printf(“Enter some integers (maximum of 20): \n”); 
       }
    Can you spot the two errors here? (Aside from horrible variable
    naming...)

    1) Notice the braces pare after the while() loop. All this would do,
    assuming it actually worked, is print "enter some integers..." over
    and over and over...

    2) This is the real problem. You use 'n' without ever giving it a
    value. This is a "BadThing(TM)". Very very bad. First off, if you
    don't give a value to a pointer before using it, it points to some
    random location in memory. Thus, when you derefernce it, as you
    are here, you get some random result (almost always _BAD_, and
    never what you expect).

    3) I lied, there's a third one. Due to the way your braces are set
    up, this loop will go on forever, because 'n' is never changed.
    Thus, the loop will go and go and go... (or, it'll never execute,
    because the random value in 'n' fails the check).

    Quzah.

  3. #3
    Registered User
    Join Date
    Sep 2001
    Posts
    752
    //Preconditions: The first parameter is an integer array; the
    second parameter is an integer representing the number
    of elements in the array; the third parameter is the
    number that is to be deleted from the array; and the
    fourth parameter is the index from which the search for
    deletion should start.

    //Postconditions: The function deletes all elements
    whose value is equal to item starting from the index
    loc. The size of the array will decrease if one or more
    copies of item existed in the array. Therefore function
    changes the number of elements in the array as well. The
    function also returns the number of deleted items.
    int delete_elemet(int a[], int *n, int item, int loc);

    I suggest doing this with a testing program...
    Code:
    //Stick this somewhere in the code...
    void printArray (int a[], int n)
    {
     int i;
     printf ("Array: ");
     for (i = 0; i < n; i++) printf ("%d ", a[i]);
     printf ("\n");
    }
    
    // And your main could look something like this...
    int main ()
    {
     int array[] = {3, 4, 5, 4, 3, 3, 3, 2, 7, 4, 5};
     int count = 11;
     printf ("Count is %d.\n", count); should be 11.
     printArray (array, count); should be array
    
     delete_element (array, &count, 5, 0); // takes out 2 elements
     printf ("Count is %d.\n", count); should be 9.
     printArray (array, count); should be array without 5s
    
     delete_element (array, &count, 3, 1); // takes out 3 elements.  Leaves behind the first 3.
     printf ("Count is %d.\n", count); should be 6
     printArray (array, count); should be array without 5s or all but the first 3.
    
     return 0;
    }
    
    int delete_elemet(int a[], int *n, int item, int loc)
    {
     // You do this part.
    }
    I'm having a pretty hard time with modifying the code you have however, so this is the best help I can offer. Try using the code that I have, of course inserting your own code for the delete_element function, and just kinda keep working at it untill it gets right.
    Callou collei we'll code the way
    Of prime numbers and pings!

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