IDK

#include <iostream>
#include <deque>
#include <string>
#include <vector>
using namespace std;

int main()
{
    unsigned int n;
    deque<int> list = deque<int>();
    string operand1, operand2, operation;

    cin >> n;
    while (n)
    {
        cin >> operand1;
        cin >> operation;
        cin >> operand2;
        list.clear();

        if (!operation.compare("+"))
        {
            //Get size of booth numbers
            int size;
            int size1 = operand1.size();
            int size2 = operand2.size();
            int diff = 0;
            if (size1 > size2){
                size = size1;
                diff = size1 - size2;
                operand2.insert(0, diff, '0');
            } else {
                size = size2;
                diff = size2 - size1;
                operand1.insert(0, diff, '0');
            }

            int carry = 0;
            for (int i = size-1 ; i >= 0; --i) {
                // Conver chars to numbers
                int num1 = (int)operand1[i] - '0';
                int num2 = (int)operand2[i] - '0';

                // Calculate
                int result = (num1 + num2 + carry) % 10;
                carry = (num1 + num2 + carry) / 10;
                list.push_front(result);

                // If one number is bigger than the other, continue calculating with smaller number as zeroes
                if (i == 0 && carry > 0) {
                    list.push_front(carry);
                }
            }
            // Print result
            deque<int>::iterator it = list.begin();
            while (it != list.end())
                cout << *it++;
            cout << endl;
        }
        else if (!operation.compare("-"))
        {
            // Get size of booth numbers
            int size;
            int size1 = operand1.size();
            int size2 = operand2.size();
            int diff = 0;
            bool negative = false;
            // Calculate which one is bigger and insert zeroes in front of smaller one
            if (size1 > size2)
            {
                size = size1;
                diff = size1 - size2;
                operand2.insert(0, diff, '0');
            }
            else if(size1 < size2)
            {
                size = size2;
                diff = size2 - size1;
                operand1.insert(0, diff, '0');
                swap(operand1, operand2);
                negative = true;
            }
            else
            {
                // Covering case when number lengths are same
                int i = -1;
                do
                {
                    i++;
                    if (operand1[i] > operand2[i])
                    {
                        size = size1;
                        diff = size1 - size2;
                        operand2.insert(0, diff, '0');
                        break;
                    }
                    else if (operand1[i] < operand2[i])
                    {
                        size = size2;
                        diff = size2 - size1;
                        operand1.insert(0, diff, '0');
                        swap(operand1, operand2);
                        break;
                    }
                } while (operand1[i] == operand2[i]);
            }

            for (int i = size - 1; i >= 0; --i) {
                // Conver chars to numbers
                int num1 = (int)operand1[i] - '0';
                int num2 = (int)operand2[i] - '0';

                // Calculate
                int result;

                // Borrowing
                int difference = num1 - num2;
                if (difference < 0)
                {
                    int j = 1;
                    while (operand1[i - j] == 0)
                    {
                        operand1[i - j] = 9;
                        j++;
                    }
                    operand1[i - j]--;

                    num1 += 10;
                }
                result = (num1 - num2) % 10;

                list.push_front(result);
            }
            // Remove zeroes at the begining of result
            deque<int>::iterator itFix = list.begin();
            while (itFix != list.end())
            {
                if (*itFix == 0)
                {
                    *itFix++;
                    list.pop_front();
                }
                else break;
            }

            // Print result
            deque<int>::iterator it = list.begin();
            while (it != list.end())
            {
                if (negative)
                {
                    negative = false;
                    cout << -(*it++);
                }
                else cout << *it++;
            }

            cout << endl;
        }
        else if (!operation.compare("*"))
        {
            // Get size of booth numbers
            int size;
            int size1 = operand1.size();
            int size2 = operand2.size();
            int diff = 0;
            vector<int> result(size1 + size2, 0);
            for (int i = size1 - 1; i >= 0; i--)
            {
                for (int j = size2 - 1; j >= 0; j--)
                {
                    result[i + j + 1] += (operand2[j] - '0') * (operand1[i] - '0'); //single array to store intermediate values
                }
            }
            for (int i = size1 + size2-1; i >= 0; i--) {
                if (result[i] >= 10) {
                    result[i - 1] += result[i] / 10; result[i] %= 10;
                }
            }
            for (unsigned int i = 0; i < (size1 + size2); i++) {
                list.push_back(result[i]);
            }

            // Remove zeroes at the begining of result
            deque<int>::iterator itFix = list.begin();
            while (itFix != list.end())
            {
                if (*itFix == 0)
                {
                    *itFix++;
                    list.pop_front();
                }
                else break;
            }

            // Print result
            deque<int>::iterator it = list.begin();
            while (it != list.end())
                cout << *it++;
            cout << endl;
        }
        n--;
    }
    return 0;
}


//template<class T>
//void Red<T>::enqueue(const Element<T>& x)
//{
//  if (isFull()) return;
//
//  Q[tail] = x;
//  tail++;
//}
//
//template<class T>
//void Red<T>::dequeue()
//{
//  if (isEmpty()) return;
//  head++;
//}


//int main()
//{
//  unsigned int n;
//  index size;
//
//  float number;
//  Element<float> *element;
//  string command;
//
//  cin >> size;
//  Red<float> list = Red<float>(size);
//
//  cin >> n;
//  while (n)
//  {
//      cin >> command;
//      if (!command.compare("ENQUEUE"))
//      {
//          cin >> number;
//          element = new Element<float>(number);
//          list.enqueue(number);
//          cout << "Stanje reda: " << list << endl;
//      }
//      else if (!command.compare("DEQUEUE"))
//      {
//          list.dequeue();
//          cout << "Stanje reda: " << list << endl;
//      }
//      else
//      {
//          cout << "Naredba nije poznata" << endl;
//          continue;
//      }
//      n--;
//  }
//  return 0;
//}
//





//#include <iostream>
//#include "DPL.h"
//using namespace std;
//
//template<class T>
//void DLList<T>::insert_after(T& k, T& d)
//{
//  Element<T>* iter = head;
//  Element<T>* x = new Element<T>(d);
//  bool found = false;
//  while (iter->next != NULL || !found)
//  {
//      if (iter->d == k)
//      {
//          if (iter->next != NULL) {
//              x->next = iter->next;
//              x->next->prev = x;
//          }
//          iter->next = x;
//          x->prev = iter;
//          found = true;
//      }
//      if(iter->next != NULL)
//          iter = iter->next;
//      else break;
//  }
//
//  if (iter->next == NULL && !found)
//  {
//      x->next = head;
//      head->prev = x;
//      head = x;
//  }
//
//  if (x->next == NULL)
//      tail = x;
//}
//
//template<class T>
//void DLList<T>::insert_before(T& k, T& d)
//{
//  Element<T>* iter = tail;
//  Element<T>* x = new Element<T>(d);
//  bool found = false;
//  while (iter->prev != NULL || !found)
//  {
//      if (iter->d == k)
//      {
//          if (iter->prev != NULL)
//          {
//              iter->prev->next = x;
//              x->prev = iter->prev;
//          }
//          x->next = iter;
//          iter->prev = x;
//          found = true;
//      }
//      if (iter->prev != NULL)
//          iter = iter->prev;
//      else break;
//  }
//
//  if (iter->prev == NULL && !found)
//  {
//      x->prev = tail;
//      tail->next = x;
//      tail = x;
//  }
//
//  if (x->prev == NULL)
//      head = x;
//}
//
//int main()
//{
//  freopen("test.txt", "r", stdin);
//  DLList<int> list;
//
//  unsigned int n;
//  int kljuc, kljuc2;
//  string naredba;
//
//  cin >> n;
//  while (n)
//  {
//      cin >> naredba;
//      if (!naredba.compare("IF"))
//      {
//          cin >> kljuc;
//          list.insert_front(kljuc);
//          cout << list << endl;
//      }
//      else if (!naredba.compare("IBC"))
//      {
//          cin >> kljuc;
//          list.insert_back(kljuc);
//          cout << list << endl;
//      }
//      else if (!naredba.compare("IA"))
//      {
//          cin >> kljuc >> kljuc2;
//          list.insert_after(kljuc, kljuc2);
//          cout << list << endl;
//      }
//      else if (!naredba.compare("IBF"))
//      {
//          cin >> kljuc >> kljuc2;
//          list.insert_before(kljuc, kljuc2);
//          cout << list << endl;
//      }
//      else if (!naredba.compare("D"))
//      {
//          cin >> kljuc;
//          list.delete_key(kljuc);
//          cout << list << endl;
//      }
//      else
//      {
//          cout << "Naredba nije poznata";
//          continue;
//      }
//      n--;
//  }
//  return 0;
//}