CODEWITHSUNDEEP
c
user2896873
user2896873

Reputation: 45

C program is not printing correct sum

c program is not printing the correct sum. I try different numbers each time and even tried working using a variable to store the value of the index in the array at each iteration. 

#include <stdio.h>
#include <malloc.h>

//find sum using pointers

int find_sum(int *a,int n) {
    int sum=0;
    int i;
    for (i=0; i<n; i++){
        sum=sum + *(a+i);
    }

    printf("sum= %i",sum);
}

int main(){
    int n;
    printf("Enter length of array: ");
    scanf("%i",&n);

    int *a=(int *)malloc(n*sizeof(int));
    int i;
    for (i=0; i<n; i++){
        printf("Enter %i numbers",n);
        int  b=*(a+i);//used to store the value at that index.
        scanf("%i",&b);
    }

    find_sum(a,n);
    return 0;
}

the output turns out to be :

Enter length of array: 3
Enter 3 numbers1
Enter 3 numbers2
Enter 3 numbers3
sum= 0

Upvotes: 3

Views: 297

Answers (1)

Rob
Rob

Reputation: 437422

Consider the line:

int b=*(a+i);  //used to store the value at that index.

This creates a new local int called b that now contains what was at a+i (i.e. it's unknown at this point).

You then replace that local int with what the user entered:

scanf("%i",&b);

But you never go back and update a.

I might suggest:

int b;//used to store the value at that index. 
scanf("%i",&b);
*(a+i) = b;

E.g.

int main() {
    int n;
    printf("Enter length of array: ");
    scanf("%i",&n);

    int *a=(int *)malloc(n*sizeof(int));
    int i;
    for (i=0; i<n; i++) {
        printf("Enter number %i: ",n);
        int b;
        scanf("%i", &b);
        *(a+i) = b;
    }

    find_sum(a, n);

    free(a);   // if you malloc, don't forget to `free`

    return 0;
}

Or, if you don't want to deal with malloc and free (which are so easy to introduce memory errors), you can just use an array:

int main() {
    int n;
    printf("Enter length of array: ");
    scanf("%i", &n);

    int a[n];
    int i;
    for (i=0; i<n; i++) {
        printf("Enter number %i: ", n);
        scanf("%i", &a[i]);
    }

    find_sum(a, n);
    return 0;
}

Upvotes: 5

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