[Leet Code] 43. Multiply Strings

43. Multiply Strings

 

 문제 설명

 

Given two non-negative integers num1 and num2 represented as strings, return the product of num1 and num2, also represented as a string.

Note: You must not use any built-in BigInteger library or convert the inputs to integer directly.

 

 제한 사항

 

• 1 <= num1.length, num2.length <= 200
• num1 and num2 consist of digits only.
• Both num1 and num2 do not contain any leading zero, except the number 0 itself.

 

 입출력 예

 

Example 1:

Input: num1 = "2", num2 = "3"
Output: "6"

Example 2:

Input: num1 = "123", num2 = "456"
Output: "56088"

 

 Python 코드

 

Python code 

class Solution:
    def multiply(self, num1: str, num2: str) -> str:
        def str_to_int(num_str):
            num = 0
            for i, c in enumerate(num_str[::-1]):
                num += pow(10, i) * (ord(c) - ord('0'))
            return num
 
        return str(str_to_int(num1) * str_to_int(num2))

* 참고 링크 : https://wellsw.tistory.com/94?category=1054641

 

 C++ 코드

 

C ++ code

class Solution {
public:
	string multiply(string num1, string num2) {
		string res(num1.size() + num2.size(), '0');
		for (int i = num1.size() - 1; i >= 0; --i) {
			int carry = 0;
			for (int j = num2.size() - 1; j >= 0; --j) {
				int tmp = (res[i + j + 1] - '0') + (num2[j] - '0')*(num1[i] - '0') + carry;
				res[i + j + 1] = tmp % 10 + '0';
				carry = tmp/10;
			}
			res[i] += carry;
		}
		auto pos = res.find_first_not_of('0');
		if (pos == string::npos)
			return "0";
		return res.substr(pos, res.length() - pos);
	}
};

* 참고 링크 : https://blog.fearcat.in/a?ID=00850-66ef66e8-11ca-463c-82ae-c4af5cb77fae

 

 출처

 

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