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Tested Python solution for LeetCode 43 with 16 pytest cases. Generate a practice environment with lcpy.
lcpy gen -n 43 # by problem number
lcpy gen -s multiply_strings # by problem name
num1 and num2 represented as strings, return the product of num1 and num2, also represented as a string.
Note: You must not use any built-in BigInteger library or convert the inputs to integer directly.
Input: num1 = "2", num2 = "3"
Output: "6"
Input: num1 = "123", num2 = "456"
Output: "56088"
num1 and num2 consist of digits only.num1 and num2 do not contain any leading zero, except the number 0 itself.class Solution:
# Time: O(m * n)
# Space: O(m + n)
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 = (ord(num1[i]) - ord("0")) * (ord(num2[j]) - ord("0"))
total = product + result[i + j + 1]
result[i + j + 1] = total % 10
result[i + j] += total // 10
return "".join(str(x) for x in result).lstrip("0")
| Time | Space |
|---|---|
| O(m * n) | O(m + n) |