Add Large Integers as Strings | Dataford Interview Questions

Alteryx data workflows may receive numeric values whose length exceeds the limits of built-in integer types. Given two non-negative decimal integers as strings, return their exact sum as a decimal string without converting either input to an integer or using arbitrary-precision numeric libraries.

Formal Specification

Implement add_strings(a, b), where a and b are non-empty strings containing only decimal digits. Inputs may contain leading zeros. Return a string containing the canonical decimal representation of a + b, with no leading zeros unless the result is "0".

The algorithm must work for inputs much larger than native numeric types. Do not use int, float, decimal, eval, or equivalent whole-string numeric conversion. Process digits from right to left, maintaining a carry, and ensure the running time is linear in the total input length.

Constraints

1 <= len(a), len(b) <= 1,000,000
Each character is an ASCII digit from 0 through 9
Inputs represent non-negative integers and may contain leading zeros
The output must contain no leading zeros unless it is exactly "0"
Do not use whole-string numeric conversion or arbitrary-precision numeric libraries

Function Signature

def add_strings(a, b):

Your question is Add Large Integers as Strings. Start with the requirements in the Question tab.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.

Problem

Formal Specification

Constraints

1 <= len(a), len(b) <= 1,000,000
Each character is an ASCII digit from 0 through 9
Inputs represent non-negative integers and may contain leading zeros
The output must contain no leading zeros unless it is exactly "0"
Do not use whole-string numeric conversion or arbitrary-precision numeric libraries

Function Signature

def add_strings(a, b):

Your question is Add Large Integers as Strings. Start with the requirements in the Question tab.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.