C++ 大数加法：高效实现三个超大整数的求和

#include <iostream>
#include <string>
#include <algorithm>
using namespace std;

string add(string num1, string num2) {
    string result;
    int carry = 0;
    int len1 = num1.length();
    int len2 = num2.length();
    int i = len1 - 1;
    int j = len2 - 1;
    
    while (i >= 0 || j >= 0 || carry > 0) {
        int digit1 = (i >= 0) ? num1[i] - '0' : 0;
        int digit2 = (j >= 0) ? num2[j] - '0' : 0;
        int sum = digit1 + digit2 + carry;
        carry = sum / 10;
        result += to_string(sum % 10);
        i--;
        j--;
    }
    
    reverse(result.begin(), result.end());
    return result;
}

int main() {
    string num1, num2, num3;
    cin >> num1 >> num2 >> num3;
    
    string sum = add(add(num1, num2), num3);
    
    cout << sum << endl;
    
    return 0;
}