String Multiplication | Dataford Interview Questions

PlanGrid may represent large construction quantities or drawing measurements as text to avoid language-specific integer limits. Implement manual multiplication for two non-negative decimal strings without converting either input to a built-in integer type.

Return the product as a canonical decimal string with no leading zeros, except that zero must be returned as "0".

Formal Specification

Implement multiply_strings(num1, num2):

Input: Two strings containing only decimal digits, with lengths from 1 to 10^4.
Output: A string containing the exact decimal product of num1 and num2.
You may use lists, loops, character operations, and integer arithmetic on individual digits.
Do not call int() on either complete input, use floating-point arithmetic, or use a big-integer multiplication library.

Constraints

1 <= len(num1), len(num2) <= 10^4
num1 and num2 contain only decimal digit characters
Inputs may contain leading zeros
The product contains at most len(num1) + len(num2) digits
Complete-input integer conversion is not allowed

Function Signature

def multiply_strings(num1, num2):

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