C++ convert string array to integers, then sum int array - c++

Question

I need to pass an user input integer to a sumTotal(& userInt) function.
If the int is 2341 I need to sum 2+3+4+1 = 10 and return the value to main!
#include <iostream>
#include <string>
#include <vector>
using namespace std;
// The program needs to input an integer like 2341, then sum it as 2+3+4+1 + 10
// I am in putting an integer and will pass it to a funtion by &.
int main()
{
string strNumber;
int intNumber = 0;
cout << "Enter your number: ";
cin >> intNumber;
// programming the logic for sumTotal(& intNumber) function before creating
strNumber = to_string(intNumber);
cout << "Your number is: " << strNumber << endl;
cout << "Your numbers length: " << strNumber.length() << " digits" << endl;
// here I need to convert the string array to an integer array
for (int i = 0; i < strNumber.length(); ++i){
intNumber[&i] = strNumber[i] - '0';
cout << "Element [" << i << "] contains: " << strNumber[i] << endl;
}
// next a recursive function must sum the integer array
// I am taking an online course and cant afford a tutor please help!
system("pause");
return 0;
}

Answer 1

if you want recursion ,you don't need any string work,try this :
#include <iostream>
using namespace std;
int recSum(int);
int main(){
int i;
cin>>i;
cout<<recSum(i);
return 0;
}
int recSum(int i){
return i==0?0:i%10+recSum(i/10);
}
recursion on array version
#include <iostream>
using namespace std;
int recSum(int* ary,int len){
return len<0?0:ary[len]+recSum(ary,len-1);
}
int main(){
int j[]={1,2,3,4,5,6,7,8,9,10};
cout<<recSum(j,9);
}

Answer 2

A simple and efficient method is to keep the number as a string and access the digits one at a time.
Note the equation:
digit_number = digit_character - '0';
Also, knowing that when summing digits, the order is irrelevant. So, we have:
sum = 0;
for (i = 0; i < string.length(); ++i)
{
sum += string[i] - '0';
}

Answer 3

A string is an array of chars. To convert a char to an int you have to do 'char' - '0'.
I wrote a couple of versions.
Pick whichever one you like best.
#include <iostream>
#include <string>
int main()
{
std::string str = "1234";
int sum = 0;
//pre C++11
for (std::string::iterator i = str.begin(); i != str.end(); ++i)
sum += (*i - '0');
//C++11
sum = 0;
for (auto i = str.begin(); i != str.end(); ++i)
sum += (*i - '0');
//ranged-for
sum = 0;
for (const auto &i : str)
sum += (i - '0');
std::cout << "Sum: " << sum;
std::cin.get();
}