Solution: Add Strings

Explore how to add two non-negative integers represented as strings by simulating manual addition digit by digit, without converting the entire strings to numeric types. Learn to handle carry values and use pointers efficiently to solve this common math-based coding interview problem.

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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 “ ...