[LeetCode] 415. Add Strings

 Problem: https://leetcode.com/problems/add-strings/

Simulate the process of adding 2 numbers.

class Solution:
    def addStrings(self, num1: str, num2: str) -> str:
        num1 = [int(w) for w in num1]
        num2 = [int(w) for w in num2]
        
        result = []
        carry = 0
        
        while num1 or num2:
            a = num1.pop() if num1 else 0 
            b = num2.pop() if num2 else 0
            
            c = a + b + carry
            
            result.append(c % 10)
            carry = c // 10
        
        if carry:
            result.append(carry)
        
        return ''.join([str(w) for w in reversed(result)])