#43

Multiply Strings

medium· Math & Geometryruns: 0

Given two non-negative integers num1 and num2 represented as strings, return the product of num1 and num2, also represented as a string. You must not use any built-in BigInteger library or convert the inputs to integers directly.

wpm 0acc 100%time 0:000 / 657

class Solution:
    def multiply(self, num1: str, num2: str) -> str:
        if num1 == "0" or num2 == "0":
            return "0"
        m, n = len(num1), len(num2)
        result = [0] * (m + n)
        for i in range(m - 1, -1, -1):
            for j in range(n - 1, -1, -1):
                product = int(num1[i]) * int(num2[j])
                p1, p2 = i + j, i + j + 1
                total = product + result[p2]
                result[p1] += total // 10
                result[p2] = total % 10
        start = 0
        while start < len(result) and result[start] == 0:
            start += 1
        return "".join(str(d) for d in result[start:])

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