编写一个 sum 函数，返回数组中所有元素的总和

Question

#include <iostream>
#include<math.h>
using namespace std;
struct Point { //B
    double x = 0;
    double y = 0;
};

void fillArray(double box[][10]) { //D
    cout << "Insert 100 doubles: ";
    for (int i = 0; i < 10; ++i) {
        for (int j = 0; j < 10; ++j) {
            cin >> box[i][j];
        }
    }
}
int sum(int* arr, int size) { //f
    int result = 0;
    for (int i = 0; i < size; ++i)
        result += arr[i];

    return result;
}
int main() {
    double box[10][10]{}; //A
    cout << "Enter your name:";

    //C
    string name;
    cin >> name;
    cout << "Hello " << name << '\n';

    fillArray(box);
    
}

I am having troubles making a couple other functions.

G)Write a difference function that receives as parameter 2 elements of the array and which returns the difference between element a and element b.

this is the first function I do not understand.

H)Write a product function that receives as parameter 2 elements of the array and which returns the product of these elements.

Answer 1

This is my advice: Clear your basics and everything will be okay.

This is my code:

Version 1 : For summing all elements of the array:

#include <iostream>

double sum(double *arr, std::size_t lengthArr )
{
    double sum = 0;
    for(int i = 0; i < lengthArr; ++i)
    {
        sum += arr[i];
        
    }
    
    //return the sum 
    return sum;
}
int main()
{
    //create the array 
    double arr[] = {1, 10, 13, 43,43,543,63};
    
    std::cout<<"The sum is: "<<sum(arr, sizeof(arr)/sizeof(double));//call the sum fuction passing the arr and its size

    return 0;
}

Version 2 : For writing a product function that receives as parameter 2 elements of the array and which returns the product of these elements.

#include <iostream>

double product(double &a, double &b )//a and b are passed by reference
{
   
    //return the product 
    return a * b;
}
int main()
{
    //create the array 
    double arr[] = {1, 10, 13, 43,43,543,63};
    
    std::cout<<"The product is: "<<product(arr[1], arr[3]);//call the product function and pass whichever elements of the array

    return 0;
}

I suppose you can modify version 2 for subtraction purpose.

Note that we can also use templates to make this program more general. These samples were just to get you started(or as a reference).