#include<iostream>
#include<cstdio>
#include<string>
#include<ctime>
using namespace std;

string Hadd(string A, string B) {
	int Len = max(A.size(), B.size());
	int a[256] = { 0 }, b[256] = { 0 };
	for (int i = A.size() - 1; i >= 0; i--) {
		a[A.size() - 1 - i] = A[i]-48;
	}
	for (int i = B.size() - 1; i >= 0; i--) {
		b[B.size() - 1 - i] = B[i] - 48;
	}
	int temp[257] = { 0 };
	for (int i = 0; i < Len; i++) {
		temp[i] += a[i] + b[i];
		temp[i + 1] = temp[i] / 10;
		temp[i] = temp[i] % 10;
	}
	string ans;
	for (int i = Len; i >= 0; i--) {
		if (i == Len && temp[i] == 0)continue;
		ans += temp[i] + 48;
		//cout << temp[i];
	}
	return ans;
}

string Hmul(string A, string B) {//高精度乘法
	int Len = max(A.size(), B.size());
	int a[256] = { 0 }, b[256] = { 0 };
	for (int i = A.size() - 1; i >= 0; i--) {//逆位存储
		a[A.size() - 1 - i] = A[i] - 48;
	}
	for (int i = B.size() - 1; i >= 0; i--) {
		b[B.size() - 1 - i] = B[i] - 48;
	}
	int temp[512] = {0};
	for (int i = 0; i <= A.size() - 1; i++) {
		for (int j = 0; j <= B.size() - 1; j++) {//运算部分
			temp[i + j] += a[i] * b[j];
			int n = i + j;
			while (temp[n] >= 10) {
				temp[n + 1] = temp[n] / 10;//每一步都控制每一位均为个位数
				temp[n] = temp[n] % 10;
				n++;
			}
		}
	}
	string ans;
	int f = 1;
	for (int i = 511; i >= 0; i--) {
		if (temp[i] == 0 && f == 1) {//除去先导0
			continue;
		}
		else {
			f = 0;
		}
		ans += temp[i] + 48;//将答案填入字符串
		//cout << temp[i];
	}
	return ans;
}

int main() {
	cout << Hmul("1144", "1910");
	return 0;
}

非常感谢大佬 例如如果我输入1145141919810的话，答案与计算器的结果不同，而如果输入1111则答案为121，求助。