高精度乘法

#include <iostream>
#include <cmath>
#include <queue>
#include <cstring>
#include <algorithm>
using namespace std;

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);

    string A, B;
    cin >> A >> B;
    if (A == "0" || B == "0") {
        cout << 0 << endl;
        return 0;
    }
    int len_A = A.size(), len_B = B.size();
    int len_res = len_A + len_B;
    int a[len_A], b[len_B], res[len_res];
    
    memset(res, 0, sizeof(res));
    for (int i = len_A - 1, j = 0; i >= 0; i--, j++) {
        a[j] = A[i] - '0';
    }
    for (int i = len_B - 1, j = 0; i >= 0; i--, j++) {
        b[j] = B[i] - '0';
    }
    for (int i = 0; i < len_B; i++) {
        for (int j = 0; j < len_A; j++) {
            res[i + j] += b[i] * a[j];
        }
    }
    for (int i = 0; i < len_res - 1; i++) {
        res[i + 1] += res[i] / 10;
        res[i] %= 10;
    }
    if (!res[len_res - 1]) {
        len_res--;
    }
    for (int i = len_res - 1; res[i] == 0; i--) {
        len_res--;
    }
    for (int i = len_res - 1; i >= 0; i--) {
        cout << res[i];
    }
    cout << endl;
    return 0;
}

来源：CSDN

作者：天亮就睡觉

链接：https://blog.csdn.net/weixin_43971049/article/details/104005324