43. Multiply Strings(unsolved)

最新推荐文章于 2022-05-14 22:34:54 发布

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本文介绍了一种不使用内置大数库或直接转换为整数的方法来计算两个非负整数的乘积。通过逐位相乘并考虑进位的方式，实现了两个字符串形式的大数之间的乘法运算。

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

Note:

The length of both num1 and num2 is < 110.
Both num1 and num2 contains only digits 0-9.
Both num1 and num2 does not contain any leading zero.
You must not use any built-in BigInteger library or convert the inputs to integer directly.

解答：

这道题还没有理解，还需要再看看

class Solution {
public:
    string multiply(string num1, string num2) {
    string sum(num1.size() + num2.size(), '0');
    for (int i = num1.size() - 1; 0 <= i; --i) {
        int carry = 0;
        for (int j = num2.size() - 1; 0 <= j; --j) {
            int tmp = (sum[i + j + 1] - '0') + (num1[i] - '0') * (num2[j] - '0') + carry;
            sum[i + j + 1] = tmp % 10 + '0';
            carry = tmp / 10;
        }
        sum[i] += carry;
    }

    size_t startpos = sum.find_first_not_of("0");
    if (string::npos != startpos) {
        return sum.substr(startpos);
    }
    return "0";
    }
};