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Tested Python solution for LeetCode 415 with 16 pytest cases. Generate a practice environment with lcpy.
lcpy gen -n 415 # by problem number
lcpy gen -s add_strings # by problem name
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.
Input: num1 = "11", num2 = "123"
Output: "134"
Input: num1 = "456", num2 = "77"
Output: "533"
Input: num1 = "0", num2 = "0"
Output: "0"
class Solution:
# Time: O(max(n, m))
# Space: O(max(n, m))
def add_strings(self, num1: str, num2: str) -> str:
i, j = len(num1) - 1, len(num2) - 1
digits: list[str] = []
carry = 0
while i >= 0 or j >= 0 or carry:
total = carry
if i >= 0:
total += ord(num1[i]) - ord("0")
i -= 1
if j >= 0:
total += ord(num2[j]) - ord("0")
j -= 1
carry, digit = divmod(total, 10)
digits.append(chr(ord("0") + digit))
return "".join(reversed(digits))
| Time | Space |
|---|---|
| O(max(n, m)) | O(max(n, m)) |