Multiply Strings

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Problem

Given two non-negative integers represented as strings, return their product, also as a string, without converting the entire inputs directly to integers or using a built-in big-integer library.

Examples

Example 1

Input:num1 = "2", num2 = "3"

Output:"6"

Example 2

Input:num1 = "123", num2 = "456"

Output:"56088"

Constraints

1 <= num1.length, num2.length <= 200

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How to approach it: the Math & Geometry pattern

A grab-bag of problems solved with numeric or coordinate reasoning rather than a specific data structure — matrix manipulation, simulation, and basic number theory.

Look for this pattern when

The problem operates on a 2-D grid or matrix directly (rotate, transpose, traverse in a pattern).
There's no obvious "textbook" data structure — the problem is really about careful step-by-step simulation.

Read the full Math & Geometry guide →

Video walkthroughs

Original problem on LeetCode ↗