Solution: Add Strings

Understand how to simulate elementary addition on two numeric strings by processing digits from right to left, managing carry-over without converting the entire strings into numbers. This lesson helps you implement an efficient algorithm for string-based addition with linear time and space complexity.

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Statement
Solution
- Time complexity
- Space complexity

Statement

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

You must not use any built-in library for handling large integers (such as BigInteger) or directly convert the inputs to integers.

Constraints:

$1 \leq$ num1.length, num2.length $\leq 10^3$
num1 and num2 consist of only digits.
num1 and num2 don’t have any leading zeros except for the zero itself.

Solution

The problem requires adding two non-negative integers represented as strings without directly converting them into numeric types or using built-in big integer operations. This means that if num1 = “ $284$ ” and num2 = “ $150$ ”, then while we can’t directly convert “ ...