Tags: "leetcode", "python", access_time 1-min read

Multiply Strings

Created: October 25, 2018 by [lek-tin]

Last updated: October 25, 2018

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

Example 1

Input: num1 = "2", num2 = "3"
Output: "6"

Example 2

Input: num1 = "123", num2 = "456"
Output: "56088"

Note

• The length of both num1 and num2 is < 110.
• Both num1 and num2 contain only digits 0-9.
• Both num1 and num2 do not contain any leading zero, except the number 0 itself.
• You must not use any built-in BigInteger library or convert the inputs to integer directly.

Solution

#1

class Solution:
    def multiply(self, num1, num2):
        """
        :type num1: str
        :type num2: str
        :rtype: str
        """
        if not num1 or not num2:
            return "0"
        if num1 == '0' or num2 == '0':
            return "0"

        product = 0

        num1Len = len(num1)
        num2Len = len(num2)
        print(num1Len, num2Len)
        for i in range(num1Len):
            num_1 = ord(num1[num1Len-1-i]) - ord('0')
            for j in range(num2Len):
                num_2 = ord(num2[num2Len-1-j]) - ord('0')
                product = product + (num_1 * 10**i * num_2 * 10**j)
        return str(product)

#2: second method no * operation. Create an array with the correct length and calculate each item, iteratively.

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