how to find summation of all elements of array c++

Question

I'm new to c++ but long story short , i want to write a c++ program that will accept input from user through an array and it will sum each array element input

 #include <iostream>
    #include <string>
    #include <math.h>
    using namespace std;
    int main() {
        int array[100];
        int sum;
    for(int i=0; i<100; i++){
      cout<<"Insert element "<<i<<": ";
      cin>>array[i];
      sum = array[i]+ //summ with the next array input;
cout<<sum;
      }
      return 0;
    }

means that if i enter any integer the program should be able to give the summation of the inputs in sequence from the first input to the last input

int sum = 0; and sum += array[i]; should work fine. Also you probably want to output sum only once, after the loop. — πάντα ῥεῖ
– πάντα ῥεῖ, Commented May 28, 2022 at 9:34
@willy You need to initialize the variable sum: int sum = 0; And this output cout<<sum; should be placed after the compound statement of the for loop. — Vlad from Moscow
– Vlad from Moscow, Commented May 28, 2022 at 9:37
You don't need an array to sum 100 input numbers; you need an accumulator initialized to zero and one variable you (a) read, and (b) add to your accumulator, then repeat 99 more times. — WhozCraig
– WhozCraig, Commented May 28, 2022 at 9:38
@Vlad from Moscow yes bro but every when i enter a number the program must give me a sum of the entered number with previous entered number — willy
– willy, Commented May 28, 2022 at 9:44

Jack · Accepted Answer · 2022-05-28 14:28:38Z

2

C++ standard library already has a function to do this which is std::accumulate:

#include <iostream>
#include <numeric>

int main() {
    int array[5] = {1,2,3,4,5};
    int total = std::accumulate(std::begin(array), std::end(array), 0);
    return 0;
}

If you plan to use not a full array you should use std::begin(array), std::begin(array) + amount as ranges.

answered May 28, 2022 at 14:28

Jack

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1 Comment

Goswin von Brederlow Over a year ago

You should use a std::array for a fixed size (which user input certainly isn't) or std::vector for dynamic size.

Vinayak · Accepted Answer · 2022-05-28 10:01:14Z

1

initialize your sum var to 0 initially and write sum+=array[i] instead of what you have written, there is also a limitation in this program as value of sum after all user input should be <=10^9 as int datatype store no. approximately upto 10^9 so take note of this fact also. Write cout<<sum<<endl; instead to be able to distinguish till previous input sum to the new input sum. Hope this will help.

answered May 28, 2022 at 10:01

Vinayak

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Comments

Goswin von Brederlow · Accepted Answer · 2022-05-28 16:59:19Z

1

You can use a do while loop:

#include<iostream>
#include<string>
#include<math.h>

int main()
{
    int array[100];
    int sum=0;
    int i=0;
    std::cout<<"Insert element"<<" "<<i<<": ";
    std::cin>>array[i];
    do
    { 
        sum=sum+array[i];
        std::cout<<sum<<std::endl;
        i++;
        std::cout<<"Insert element"<<" "<<i<<": ";
    }while(std::cin>>array[i]);
    return 0;
}

edited May 28, 2022 at 16:59

Goswin von Brederlow

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answered May 28, 2022 at 14:24

Vaibhav Vishal Singh

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1 Comment

Goswin von Brederlow Over a year ago

This will fail if I want the sum of 0 elements since the first input isn't checked.

Goswin von Brederlow · Accepted Answer · 2022-05-28 17:03:46Z

1

If all you want is the sum then just compute the sum. No need to store anything:

#include <iostream>
#include <string>
#include <math.h>

int main() {
    int sum = 0;
    for(int i=0; i<100; i++){
        std::cout << "Insert element " << i << ": ";
        int t;
        std::cin >> t;
        sum += t
        std::cout << sum;
    }
}

answered May 28, 2022 at 17:03

Goswin von Brederlow

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