Big Integer

Big Integer, 带小数的加法。 好恶心啊！先按照小数点. 来split两部分。然后先加小数，然后把小数可能的进位丢进整数部分一起算。

class Solution(object):
    def add(self, num1, num2):
        if '.' in num1 and '.' in num2:
            inte1, deci1 = num1.split('.')
            inte2, deci2 = num2.split('.')   
        decimal, carry = self.doDeci(deci1, deci2)
        integer = self.doInt(inte1, inte2, carry)

        return '.'.join([integer, decimal])

    def doDeci(self, num1, num2):
        num1 = list(map(int, list(num1)))
        num2 = list(map(int, list(num2)))
        if len(num1)<len(num2):
            num1, num2 = num2, num1

        carry = 0
        for i in range(len(num2)-1, -1, -1):
            tmp = num2[i] + num1[i] + carry
            num1[i] = tmp%10
            carry = tmp//10

        res = list(map(str, num1))
        return ''.join(res), carry

    def doInt(self, num1, num2, carry):
        num1 = list(map(int,num1))[::-1]
        num2 =list(map(int,num2))[::-1]
        if len(num1)<len(num2):
            num1, num2 = num2, num1

        index = 0
        while index<len(num1):
            n2 = int(num2[index]) if index<len(num2) else 0
            tmp = n2 + num1[index] + carry
            num1[index] = tmp%10
            carry = tmp//10
            index += 1

        if carry: num1.append(1)
        num1 = list(map(str, num1))
        return ''.join(num1[::-1])


num1 = '20.78'
num2 = '1.5679'
so = Solution()
ans = so.add(num1, num2)
print(ans)

不带小数的加法和乘法。

class Solution(object):
    def add(self, num1, num2):
        """
        :type num1: str
        :type num2: str
        :rtype: str
        """
        num1 = list(num1)[::-1]
        num2 = list(num2)[::-1]

        if len(num1)<len(num2):
            num1, num2 = num2, num1

        carry = 0
        index = 0
        while index<len(num1):
            n2 = int(num2[index]) if index<len(num2) else 0
            tmp = n2 + int(num1[index]) + carry
            cur = tmp%10
            carry = tmp//10
            num1[index] = str(cur)
            index += 1

        if carry: num1.append('1')

        return ''.join(num1[::-1])

    def multiply(self, num1, num2):
        """
        :type num1: str
        :type num2: str
        :rtype: str
        """
        num1 = num1[::-1]
        num2 = num2[::-1]

        res = [0]*(len(num1) + len(num2))
        for i in range(len(num2)):
            for j in range(len(num1)):
                tmp = int(num2[i])*int(num1[j])
                res[j+i] += tmp
                res[j+i+1] += res[j+i]//10
                res[j+i] = res[j+i]%10

        while len(res)>1 and res[-1]==0:
            res.pop()

        return ''.join(map(str,res))[::-1]

num1 = '124'
num2 = '5679'
so = Solution()
a = so.add(num1, num2)
print(a)
a = so.multiply(num1, num2)
print(a)