How can I add up the values of the individual digits in a string?-CodePudding

I want to get the sum of the individual digits of an ID entered by the user. So far this is the code I have, and my code can count the number of characters in the user input but I'd like for it to also calculate the sum of the individual digits.

cout << "Type in your student login ID: "; // user prompt for student id
string studentId;
getline(cin, studentId); // user input of student ID

cout << "Student ID Sum: " << studentId.length() << endl; // computer output of studentId

CodePudding user response：

Just use the range based for loop. As for example

unsigned int sum = 0;

for ( const auto &c : studentId )
{
    if ( '0' <= c && c <= '9' ) sum  = c - '0';
}

CodePudding user response：

You can take advantage of std::accumulate from <numeric> for this purpose, iterating over the string s and adding the numeric value of each character to an accumulator if it's a digit.

#include <string>
#include <iostream>
#include <numeric>
#include <cctype>

int main() {
  std::string s = "456";

  std::cout << std::accumulate(
    s.begin(), s.end(), 0,
    [](unsigned int i, char &ch){ return std::isdigit(ch) ? i   (ch - '0') : i; }
  ) << std::endl;

  return 0;
}

Prints:

CodePudding user response：

You can do calculate sum by using a for loop.

#include <iostream> 
using namespace std;
int main()
{
    //Initializing variables.
    char studentId[100];
    int i,sum = 0;
    getline(cin, studentId); //get user input here in array
    
    //Iterating each character through for loop.
    for (i= 0; studentId[i] != '\0'; i  )
    {
        if ((studentId[i] >= '0') && (studentId[i] <= '9'))  //Checking for numeric characters.
        {
            sum  = (studentId[i] - '0'); //Adding numeric characters.
        }
    }
    //Printing result.
    cout<<"Sum of the studentId:"<< sum;
    return 0; 
}