DIY: Multiply Strings

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.

Constraints

• 1 <= num1.length, num2.length <= 200
• num1 and num2 consist of digits only.
• The num1 and the num2 do not contain any leading zero, except the number 0 itself.

Input

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

num1 = 5
num2 = 6

Output

The following is the output of the above input:

30

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.