在 C++ 中查找数字的总和。 不同的方法

Question

I am new to c++ and having trouble with a simple programme I need to find the sum of digits I can do that in python but I don't know how to do the same in c++.

digits = "1234"
sum = 0
for digit in digits:
    sum += int(digit)
print(sum)

How to do the same in c++?

I tried to do the same in c++ but ends up in a error.

string digits = "1234";
int sum, i;
for(i=0;i<digits.length();i++){
    sum += stoi(digits[i]);
}

But this doesn't work

Answer 1

string digits = "1234";
int sum = 0;
for(int i = 0; i < digits.length(); i++){
    sum += digits[i] - '0';
}

Characters have their numbers ( ord ). By working with characters in C++ you actually work with these numbers (so char is an integer type). For '0' it's some number, for '1' it's 1 + '0' , for '2' it's 2 + '0' and so on. So by subtracting '0' you get the right digit.