43. Multiply Strings

Approach 1: Do it like we do it in Elementary school

class Solution(object):
def multiply(self, num1, num2):
"""
https://leetcode.com/problems/multiply-strings/description/
:type num1: str
:type num2: str
:rtype: str
"""
# return str(int(num1)*int(num2))
num1 = num1.encode('ascii','ignore')
num2 = num2.encode('ascii','ignore')
su = 0
i = 0
le2 = len(num2)
while i < le2:
su1 = 0
a = int(num2[i])
for j in num1:
# print(a, j)
su1 += int(j) * a
su1 *= 10
su += su1
su *= 10
i += 1
return str(su/100)
‚Äč

Time Complexity: O(N*M) where M and N are the lengths of the 2 strings

Space Complexity: O(1)