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multiply-strings.py
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multiply-strings.py
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# V0
class Solution(object):
def multiply(self, num1, num2):
"""
:type num1: str
:type num2: str
:rtype: str
"""
if num1 == '0' or num2 == '0':
return '0'
ans = 0
for i, n1 in enumerate(num2[::-1]):
plus = 0
curr = 0
for j, n2 in enumerate(num1[::-1]):
multi = (ord(n1) - ord('0')) * (ord(n2) - ord('0'))
first, second = multi // 10, multi % 10
curr += (second + pre) * (10 ** j)
plus = first
curr += plus * (10 ** len(num1))
ans += curr * (10 ** i)
return str(ans)
# V0'
# AGAIN
# class Solution(object):
# def multiply(self, num1, num2):
# """
# :type num1: str
# :type num2: str
# :rtype: str
# """
# num1, num2 = num1[::-1], num2[::-1]
# res = [0] * (len(num1) + len(num2))
# for i in range(len(num1)):
# for j in range(len(num2)):
# res[i + j] += int(num1[i]) * int(num2[j])
# res[i + j + 1] += res[i + j] / 10
# res[i + j] %= 10
#
# # Skip leading 0s.
# i = len(res) - 1
# while i > 0 and res[i] == 0:
# i -= 1
#
# return ''.join(map(str, res[i::-1]))
# V1
# https://blog.csdn.net/fuxuemingzhu/article/details/80681702
# https://blog.csdn.net/XX_123_1_RJ/article/details/81431630
# DEMO : ORD
# In [24]: n1='1'
# In [25]: n2='2'
# In [26]: (ord(n1) - ord('0'))
# Out[26]: 1
# In [27]: (ord(n2) - ord('0'))
# Out[27]: 2
# In [28]: ord(n1)
# Out[28]: 49
# In [29]: ord(n2)
# Out[29]: 50
# In [30]: ord('0')
# Out[30]: 48
class Solution(object):
def multiply(self, num1, num2):
"""
:type num1: str
:type num2: str
:rtype: str
"""
if num1 == '0' or num2 == '0':
return '0'
ans = 0
for i, n1 in enumerate(num2[::-1]):
pre = 0
curr = 0
for j, n2 in enumerate(num1[::-1]):
multi = (ord(n1) - ord('0')) * (ord(n2) - ord('0'))
first, second = multi // 10, multi % 10
curr += (second + pre) * (10 ** j)
pre = first
curr += pre * (10 ** len(num1))
ans += curr * (10 ** i)
return str(ans)
# V1'
# https://blog.csdn.net/fuxuemingzhu/article/details/80681702
# https://blog.csdn.net/XX_123_1_RJ/article/details/81431630
class Solution(object):
def multiply(self, num1, num2):
"""
:type num1: str
:type num2: str
:rtype: str
"""
return str(int(num1) * int(num2))
# V1''
# https://www.jiuzhang.com/solution/multiply-strings/#tag-highlight-lang-python
class Solution:
"""
@param num1: a non-negative integers
@param num2: a non-negative integers
@return: return product of num1 and num2
"""
def multiply(self, num1, num2):
# write your code here
len1, len2 = len(num1), len(num2)
dig1 = dig2 = 0
for i in range(len1):
dig1 = dig1 * 10 + ord(num1[i]) - ord('0')
for i in range(len2):
dig2 = dig2 * 10 + ord(num2[i]) - ord('0')
return str(dig1*dig2)
# V2
# Time: O(m * n)
# Space: O(m + n)
class Solution(object):
def multiply(self, num1, num2):
"""
:type num1: str
:type num2: str
:rtype: str
"""
num1, num2 = num1[::-1], num2[::-1]
res = [0] * (len(num1) + len(num2))
for i in range(len(num1)):
for j in range(len(num2)):
res[i + j] += int(num1[i]) * int(num2[j])
res[i + j + 1] += res[i + j] / 10
res[i + j] %= 10
# Skip leading 0s.
i = len(res) - 1
while i > 0 and res[i] == 0:
i -= 1
return ''.join(map(str, res[i::-1]))
# Time: O(m * n)
# Space: O(m + n)
# Using built-in bignum solution.
class Solution2(object):
def multiply(self, num1, num2):
"""
:type num1: str
:type num2: str
:rtype: str
"""
return str(int(num1) * int(num2))