2020-08-13

43. 字符串相乘

题解: 模拟两个字符串相乘的过程，字符串A第i位和B第j位的相乘结果在结果C的第 i+j+1位(从0开始计数)

class Solution(object):
    def multiply(self, num1, num2):
        """
        :type num1: str
        :type num2: str
        :rtype: str
        """
        ans = [0]*(len(num1)+len(num2))
        for i in range(len(num1)-1, -1, -1):
            for j in range(len(num2)-1, -1, -1):
                ans[i+j+1] += int(num1[i]) * int(num2[j])
                if ans[i+j+1]>=10: ans[i+j] += ans[i+j+1]/10
                ans[i+j+1]%=10
        
        ans = map(str, ans)
        ans =  "".join(ans).lstrip("0") 
        return ans if len(ans) else "0"