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415. Add Strings

Math String Simulation

Problem - Add Strings

Easy

Given two non-negative integers, num1 and num2 represented as string, return the sum of num1 and num2 as a string.

You must solve the problem without using any built-in library for handling large integers (such as BigInteger). You must also not convert the inputs to integers directly.

 

Example 1:

Input: num1 = "11", num2 = "123"
Output: "134"

Example 2:

Input: num1 = "456", num2 = "77"
Output: "533"

Example 3:

Input: num1 = "0", num2 = "0"
Output: "0"

 

Constraints:

  • 1 <= num1.length, num2.length <= 104
  • num1 and num2 consist of only digits.
  • num1 and num2 don't have any leading zeros except for the zero itself.

Solutions

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class Solution:
    def addStrings(self, num1: str, num2: str) -> str:
        i, j = len(num1) - 1, len(num2) - 1
        result = []
        carry = 0
        while i >= 0 or j >= 0 or carry:
            val1 = 0 if i < 0 else (ord(num1[i]) - ord("0")) 
            val2 = 0 if j < 0 else (ord(num2[j]) - ord("0")) 
            carry, val = divmod(val1 + val2 + carry, 10)
            result.append(str(val))
            i, j = i - 1, j - 1
        return "".join(result[::-1])

Submission Stats:

  • Runtime: 5 ms (58.18%)
  • Memory: 18.1 MB (53.58%)