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

• πάντα ῥεῖ: int sum = 0; and sum += array[i]; should work fine. Also you probably want to output sum only once, after the loop.
• Vlad from Moscow: @willy Are you going to input 100 values?:)
• Vlad from Moscow: @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.
• WhozCraig: 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.
• willy: @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

Answer 1

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.

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

Answer 2

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.

Answer 3

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;
}

• Goswin von Brederlow: This will fail if I want the sum of 0 elements since the first input isn't checked.

Answer 4

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;
 }
}