43. Multiply Strings

solution43.py

# https://leetcode.com/problems/multiply-strings/description/

class Solution(object):
    def multiply(self, num1, num2):
        """
        :type num1: str
        :type num2: str
        :rtype: str
        """
        temp_values = []
                
        num1 = num1[::-1]
        num2 = num2[::-1]
                
        for n1 in num1:
            carry = 0
            temp = ['0'] * len(temp_values)
            a = int(n1)
            
            for n2 in num2:
                b = int(n2)
                c = (a * b) + carry
                temp.append(str(c % 10))
                carry = c // 10
            if carry != 0:
                temp.append(str(carry))
            temp_values.append(''.join(temp))
        
        total = ""
        
        for v in temp_values:
            total = add_rev_num_strs(total, v)
            
        total = total[::-1]
        for digit in total:
            if digit != '0':
                return total
            
        return '0'
    
def add_rev_num_strs(a, b):
    a_ptr = b_ptr = 0
    carry = 0
    result = []
    
    while a_ptr < len(a) or b_ptr < len(b):
        temp_a = 0
        temp_b = 0
        if a_ptr < len(a):
            temp_a = int(a[a_ptr])
        if b_ptr < len(b):
            temp_b = int(b[b_ptr])
        temp = temp_a + temp_b + carry
        result.append(str(temp % 10))
        carry = temp // 10
        a_ptr += 1
        b_ptr += 1
    
    if carry != 0:
        result.append(str(carry))
    
    return ''.join(result)