DIY: Multiply Strings

Solve the interview question "Multiply Strings" in this lesson.

Problem statement

You are given two non-negative integers represented as strings. Your task is to find the product of the given two integer numbers in the form of a string. For this, you will first convert the given strings to an integer without using the built-in library and then use the multiplication operator.


  • 1 <= firstNumber.length, secondNumber.length <= 200
  • firstNumber and secondNumber consist of digits only.
  • The firstNumber and the secondNumber do not contain any leading zero, except the number 0 itself.


The inputs to the function are strings with integer values. The following is an example input:

firstNumber = 5
secondNumber = 6


The following is the output of the above input:


Coding exercise

Implement the function multiply(num1, num2), which accepts two string arguments num1 and num2 storing non-negative integer numbers and returns the product of the two integers as a string.

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