#include <iostream>
#include <array>
#include <sstream>
#include <string>
#include <fstream>
#include <vector>

int bignumb(std::string numb);

std::vector <int> answer;
std::vector <int>::iterator answer_it;

int numb_array[50];

int main(){

  std::ifstream numblist;
  numblist.open("numberlist.txt");

  if (!numblist){
    std::cout << "File not found" << std::endl;
    return 0;
  }
  else{
    int i = 1;
    for(std::string line; numblist >> line; i++){
      bignumb(line);
    }
  }

  std::cout << "ANSWER : ";
  for (int i = 0; i < 10; i++){
    std::cout << answer[i];
  }
}

int bignumb(std::string numb){

  bool carry_over = false;
  int answer_count = answer.size()-1;
  int k = 0;

  for(std::string::iterator i = numb.begin(); i !=  numb.end(); i++){
    char a = *i;
    int b = (int)a - '0';
    numb_array[k] = b;
    k++;
  }

  if (answer.empty() == true){
    for (int i = 0; i != 50; i++){
      int a = numb_array[i];
      answer.push_back(a);
    }
  }
  else{
    int ans_index = answer.size() - 50;

    for (int i = 49; i != -1; i--){
      int a = numb_array[i];
      int b = answer[ans_index + i];

      if (carry_over == true){
    if      (a + b + 1 == 10)     {answer[answer_count] = a + b - 9;      carry_over = true; }
    else if (a + b + 1 < 10 )     {answer[answer_count] = a + b + 1;      carry_over = false;}
      }
      else if (carry_over == false){
    if (a + b >= 10)              {answer[answer_count] = a + b - 10;     carry_over = true; }
    else                          {answer[answer_count] = a + b;          carry_over = false;}
      }
      answer_count--;
    }
  }

  if (carry_over == true && answer.size() - 50 != -1){
    if (answer.size() == 50)                   {answer.insert(answer.begin(), 1);}

    else{
      for(int i = answer.size() - 50; carry_over == true && i != -1; i--){
    if      (i == 0 && carry_over == true) {answer.insert(answer.begin(), 1);}
        else if (answer[i-1] + 1 == 10)        {answer[i-1] = 0;               carry_over = true; }
    else if (answer[i-1] + 1 < 10)         {answer[i-1] = answer[i-1] + 1; carry_over = false;}
      }
    }
  }
}

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