LeetCode 刷题记录 43. Multiply Strings

最新推荐文章于 2021-07-31 10:38:31 发布

dldldl1994

最新推荐文章于 2021-07-31 10:38:31 发布

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分类专栏： LeetCode

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这篇博客介绍了如何解决LeetCode上的43题——字符串乘法问题。提供了两种解法，一种是暴力法，按照乘法运算规则逐位相乘；另一种是优化方法，通过从后往前遍历，利用索引来确定结果的高位和低位。在实现过程中需要注意溢出问题和去除结果中的前置0。示例代码分别用C++、Java和Python给出。

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

Example 1:

Input: num1 = “2”, num2 = “3”
Output: “6”
Example 2:

Input: num1 = “123”, num2 = “456”
Output: “56088”
Note:

The length of both num1 and num2 is < 110.
Both num1 and num2 contain only digits 0-9.
Both num1 and num2 do not contain any leading zero, except the number 0 itself.
You must not use any built-in BigInteger library or convert the inputs to integer directly.
解法1：
暴力法：

模仿乘法的规则，从num2的最后一位开始，依次与num1相乘，然后在后面补0，然后将所有的数加起来即可

class Solution {
public:
    string multiply(string num1, string num2) {
        if(num1 == "0" || num2 == "0"){
            return "0";
        }
        string ans = "0";
        int index = 0;
        int n = num1.size() - 1;
        int m = num2.size() - 1;
        for(int i = m; i >= 0; i--){
            int carry = 0;
            int m1 = num2[i] - '0';
            string temp = "";
            for(int j = n; j >&

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