Question

i am a bit confused in using array in doing recursion, can anyone correct my mistake?

new update, based on question required some of the line cannot be edit

double sum_of_array(double x[],int size)
{
    static double sum; <---can be edit
    int index = 0; <--can be edit

    if(index<size){
        return sum + sum_of_array(x,size-1); <--can be edit
    } else {
       something ; <--can be edit
       return sum; <--can be edit
    }
}

int main(void){
    double x[] = {4.5,5.0,6.8};
    double y[] = {4.7,3.4,2.5,5.2};

    cout<<"Sum X = "<<sum_of_array(x,3)<<endl;
    cout<<"Sum Y = "<<sum_of_array(y,4)<<endl;

    return 0;
}

output:

Sum of the element in X[]=15.3

Sum of the element in Y[]= 15.8

Answer 1

You never actually add the values in x[] and y[] to sum and in addition, index is always equal to 0. You should probably pass it as another parameter to the function:

double sum_of_array(double x[], int size, int index)
{
    if(index<size){
        return x[index] + sum_of_array(x, size, index+1); 
    }
    else {
        return 0;
    }
}

You don’t actually need the sum variable.