CODEWITHSUNDEEP
carrayspointerssum
nicoolaslb
nicoolaslb

Reputation: 67

Sum of two arrays using pointers in C

I am trying to create a program in C that calculates the sum of two int arrays using pointers. Here is an example of what I want to do:

int a[] = {1,2,3,4}
int b[] = {1,2,3,4,5,6}
int c[] = sumArrays(a,b,4,6)
Output : c = {2,4,6,8,5,6}

The problem is my output is different, it shows:

Output : c = {2,4,6,8}

Any idea what did I do wrong and how to correct it ? Here is my code :

#include <stdio.h>
#include <stdlib.h>

int* sumArrays(int *arr1, int *arr2, int dim1,int dim2)
{
    int *ret = NULL;

    if(dim1<dim2) ret = (int*) malloc(dim2*sizeof(int));
    else ret =  (int*) malloc(dim1*sizeof(int));
    if(ret)
    {
        if(dim1<dim2) {
            int i = 0;
            for (i = 0;i < dim1;i++) {
                ret[i] = arr1[i] + arr2[i];
            }
            for (i = dim1; i < dim2;i++) {
                ret[i]=arr2[i];
            }   
        } else {
            int i = 0;
            for (i = 0;i < dim2;i++) {
                ret[i] = arr1[i] + arr2[i];
            }
            for (i = dim2; i < dim1;i++) {
                ret[i]=arr1[i];
            } 
        }
    }
    return ret;
}


int main()
{
int *a[] = {1,2,3,4};
int *b[] = {1,2,3,4,5,6};

int *c = sumArrays(a,b,4,6);
printf("c = ");
int i;
for (i = 0; i < sizeof(c); i++) {
    printf("%d,",c[i]);
} 
}

Upvotes: 1

Views: 7105

Answers (2)

Soner from The Ottoman Empire
Soner from The Ottoman Empire

Reputation: 20891

You have problem about using pointers. 

int *a[] = {1,2,3,4};      // a is an array of pointers to integers.
int *b[] = {1,2,3,4,5,6};  // b is an array of pointers to integers.

By doing this, you are declaring array of pointers to integers. So, it most likely causes compiler warning or error depending on your compile settings like, initialization makes pointer from integer without a cast. When you are passing the actual arguments to formal parameters, it causes same warning as well. Your main should be like this,

int main()
{
    int a[] = {1,2,3,4}; 
    int b[] = {1,2,3,4,5,6};
    int sizeA = sizeof(a) / sizeof(*a);
    int sizeB = sizeof(b) / sizeof(*b);


    int *c = sumArrays(a,b,sizeA,sizeB);
    printf("c = ");
    int i;
    for (i = 0; i < (sizeA < sizeB ? sizeB : sizeA); i++) {
        printf("%d,",c[i]);
    }
}

Upvotes: 1

Andriy Berestovskyy
Andriy Berestovskyy

Reputation: 8534

Sizeof c will always return 4 for 32-bit system and 8 for 64-bit, because c is a pointer to int.

So to print the result array you should write:

for (i = 0; i < 6; i++) {

Upvotes: 5

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