28. Multiply Strings

You’re interviewing for a backend or data engineering role at a FAANG-level company. The interviewer describes a real product scenario:

A large-scale financial or analytics platform processes extremely large numeric values represented as strings. These values may exceed the limits of built-in integer types due to high precision requirements, regulatory constraints, or cross-system compatibility.

Because of this, the platform cannot directly convert these strings into numeric data types. Instead, it needs a safe and accurate way to multiply two non-negative numbers that are provided as strings and return the result as a string.

This is a common practice coding problem for DSA question might ask in Google, Amazon, Netflix, Meta, Apple, Microsoft, Uber, and Bloomberg interviews.

Your Task

Given two non-negative integers num1 and num2 represented as strings, return their product, also represented as a string.

You must not use any built-in big integer libraries or convert the input strings directly into integers.

Input Format

• num1: a string representing a non-negative integer
• num2: a string representing a non-negative integer

Output Format

• A string representing the product of num1 and num2

Examples

Constraints

• 1 <= num1.length, num2.length <= 200
• num1 and num2 consist of digits only
• num1 and num2 do not contain leading zeros except the number "0"