Solution to Leetcode 415 Add Strings

soln_lc415.py

class Solution:
    # credit: https://www.youtube.com/watch?v=q1RR8gk47Cg
    def addStrings(self, num1: str, num2: str) -> str:
        i = len(num1) - 1
        j = len(num2) - 1
        carry = 0
        res = []
        while i >= 0 or j >= 0:
            int1 = int(num1[i]) if i >=0 else 0 
            int2 = int(num2[j]) if j >= 0 else 0
            cur_sum = carry + int1 + int2
            res.append(cur_sum % 10)
            carry = cur_sum//10
            i -= 1
            j -= 1
        if carry != 0:
            res.append(carry)
        
        final_res = [str(res[t]) for t in range(len(res)-1, -1, -1)]
        return "".join(final_res)