数据太大，爆short了，要用高精度

数据太大爆short了要用高精度
代码如下
（用int就行了）
最复杂的代码

#include<bits/stdc++.h>
using namespace std;
struct big{
	string num;
	string add(string a, string b) {
	    reverse(a.begin(), a.end());
	    reverse(b.begin(), b.end());
	    int len = max(a.length(), b.length());
	    string result;
	    int carry = 0;
	    for (int i = 0; i < len; ++i) {
	        int digitA = i < a.length() ? a[i] - '0' : 0;
	        int digitB = i < b.length() ? b[i] - '0' : 0;
	        int sum = digitA + digitB + carry;
	        result.push_back((sum % 10) + '0');
	        carry = sum / 10;
	    }
	    if (carry > 0)result.push_back(carry + '0');
	    reverse(result.begin(), result.end());
	    return result;
	}
	string subtract(string a, string b) {
	    if (a.length() < b.length() || (a.length() == b.length() && a < b)) {
	        swap(a, b);
	        return "-" + subtract(a, b);
	    }
	
	    reverse(a.begin(), a.end());
	    reverse(b.begin(), b.end());
	
	    string result;
	    int borrow = 0;
	
	    for (int i = 0; i < a.length(); ++i) {
	        int digitA = a[i] - '0';
	        int digitB = i < b.length() ? b[i] - '0' : 0;
	
	        int diff = digitA - digitB - borrow;
	        if (diff < 0) {
	            diff += 10;
	            borrow = 1;
	        } else {
	            borrow = 0;
	        }
	        result.push_back(diff + '0');
	    }
	    while (result.length() > 1 && result[0] == '0')result.erase(0, 1);
	    reverse(result.begin(), result.end());
	    return result;
	}
	string multiply(string a, string b) {
	    if (a == "0" || b == "0") return "0";
	
	    reverse(a.begin(), a.end());
	    reverse(b.begin(), b.end());
	    int len = a.length() + b.length();
	    vector<int> result(len, 0);
	
	    for (int i = 0; i < a.length(); ++i) {
	        for (int j = 0; j < b.length(); ++j) {
	            int digitA = a[i] - '0';
	            int digitB = b[j] - '0';
	            result[i + j] += digitA * digitB;
	        }
	    }
	    for (int i = 0; i < len - 1; ++i) {
	        int carry = result[i] / 10;
	        result[i + 1] += carry;
	        result[i] %= 10;
	    }
	    string resultStr;
	    for (int i = len - 1; i >= 0; --i) {
	        if (resultStr.empty() && result[i] == 0) continue;
	        resultStr.push_back(result[i] + '0');
	    }
	    return resultStr.empty() ? "0" : resultStr;
	}
};
int main(){
	big a;
	cout<<a.multiply("3456","1234");
}