Please help! I am so lost as to how to fix this!

[blackfox_1109]

I am relatively new to programming, and I have been working on this program for several days. I have gotten all my functions to work perfectly, except for my intAdd function, and I cant seem to figure out where it is going wrong or how to fix it.

The intAdd function adds two very large integers together, by putting each digit of the large integer in an array, putting the arrays into reverse order, and adding them together.

An example of this would be

12345+1

[5][4][3][2][1]
+[1]
_____________
[6][4][3][2][1]

so that when it is flipped back to normal again, it is 12346.



When I try to run the function however, it does not add it correctly. It seems to fill the entire array with zeros except for the one's place, and I cant see why this is happening or how I can fix it.


Any advice as to what is causing this and how I may possibly fix this would be greatly appreciated.

Here is the header file with the function and structure definition:

typedef struct HugeInteger
{
 // a dynamically allocated array to hold the digits of a huge integer
 int *digits;
 // the number of digits in the huge integer (approx. equal to array length)
 int length;
} HugeInteger;

// Functional Prototypes
HugeInteger *hugeAdd(HugeInteger *p, HugeInteger *q);

and here is the function that is causing me trouble:

//create function for hugeAdd
HugeInteger *hugeAdd(HugeInteger *p, HugeInteger *q){
int i;
//return NULL if either pointer is NULL
if(p == NULL || q == NULL)
    return NULL;
//create a new HugeInteger to store the result in
HugeInteger *a = NULL;
HugeInteger *trim = NULL;

a = malloc(sizeof(HugeInteger));
trim = malloc(sizeof(HugeInteger));
//check if malloc was successful
if(a == NULL){
    printf("\n23: Malloc failed\n");
    return NULL;
}
a->digits = NULL;
//if p is bigger than q
if (p->length > q->length){
    a->digits = calloc(p->length+1, sizeof(int));
    a->length = p->length;
    //check to make sure calloc was successful
    if(a->digits == NULL){
        printf("\n34: Calloc failed\n");
        a->length = 0;
        free(a);
        return NULL;
    }
    //to find where the error occurs with the addition
    printf("\np contains the elements: \t\t\t");
    for(i=0; i<p->length; i++)
        printf("%d",p->digits[i]);
    printf("\nq contains the elements: \t\t\t");
    for(i=0; i<q->length; i++)
        printf("%d", q->digits[i]);

    for (i=0; i<q->length; i++){
        //if sum is >10 do this, since each cell should only hold 0-9
        if (p->digits[i]+q->digits[i]>=10){
            a->digits[i] += (p->digits[i]+q->digits[i])-10;
            a->digits[i+1] = 1;
        }
        else{
            a->digits[i] += p->digits[i]+q->digits[i];
        }
    }
}
//if q is bigger than p
else{

    a->digits = calloc(q->length+1, sizeof(int));
    a->length = q->length;
    //check to make sure calloc was successful
    if(a->digits == NULL){
        printf("\n62: Calloc Failed\n");
        a->length = 0;
        free(a);
        return NULL;
    }
    for (i=0; i<p->length; i++){
        //if sum is >10 do this, since each cell should only hold 0-9
        if (p->digits[i]+q->digits[i]>=10){
            a->digits[i] += (p->digits[i]+q->digits[i])-10;
            a->digits[i+1] += 1;
        }
        else{
            a->digits[i] += p->digits[i]+q->digits[i];
        }
    }
}
//if there is a hanging 0 at the end
    if (a->digits[a->length] == 0)
    {
        trim->digits = malloc(sizeof(a->length-1));
        if(trim->digits == NULL)
        {
            printf("\ntrim malloc failed");
            free(trim);
            return NULL;
        }
        //transfer digits over to new struct
        for (i=0; i<a->length-1; i++)
        {
            trim->digits[i] = a->digits[i];
        }
        trim->length = a->length-1;
        /*  Dont know why I have this
        for(i=0; i<trim->length; i++)
        {
            trim->digits[i]=a->digits[i];
            free(a->digits);
            free(a);
        }
        */
    printf("\nHere is the result of the Addition function (still in reverse):\t");
//to determine where the error is occurring
    for (i=0; i<trim->length; i++)
        printf("%d", trim->digits[i]);
    return trim;
    }
return a;
}

Please tell me what is causing this issue! Thank you so much!

[GReaper]

You forget to copy the extra digits to "a" from "p" and "q".