Leetcode 415 Solution

This article provides solution to leetcode question 415 (add-strings)
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https://leetcode.com/problems/add-strings

Solution

class Solution {
public:
    string addStrings(string num1, string num2) {
        string res;

        auto it1 = num1.rbegin();
        auto it2 = num2.rbegin();

        int carry = 0;
        while (it1 != num1.rend() || it2 != num2.rend())
        {
            int val = carry;

            if (it1 != num1.rend())
                val += *it1++ - '0';

            if (it2 != num2.rend())
                val += *it2++ - '0';

            if (val >= 10)
            {
                val -= 10;
                carry = 1;
            }
            else
                carry = 0;

            res += to_string(val);
        }

        if (carry == 1)
            res += "1";

        reverse(res.begin(), res.end());
        return res;
    }
};