Need help (File) C++

[Ozzy69]

Hello, i make a code in c++ for read files.
This code read of last line until first line, but i want know if have how improve this code.
My file:
Sum: 3 4 5 6 = 18
Sum: 2 3 4 5 = 32
Sum: 3 4 5 6 = 50
Sum: 1 2 3 4 = 60
Sum: 5 6 7 = 78
Sum: 3 3 5 6 = 17
Sum: 2 2 = 4
Sum: 1 1 = 2
Sum: 68 1 = 69
Sum: 11 11 = 22
Sum: 7 7 = 14

my code:

#include <iostream>
#include <fstream>

using namespace std;

int main()
{
    int cont;
    string operacao;

    for(int i = 0; i < 10; i++){
        cont = 0;
        ifstream input("historico.txt");
        while(!input.eof()){
            getline (input,operacao);
            if(cont == 10 - i){
                cout << operacao << " ";
            }
            cont++;
        }
        cout << endl;
    }
    return 0;
}

[Jaybob66]

it would be more efficient to read the file one time only. consider that to be a data cache. then you can work backwards or forwards at the same speed.

{
    string operacao;
    vector<string> operations;

    // cache the file contents

    ifstream input("historico.txt");
    while(!input.eof())
    {
        getline (input,operacao);
        operations.push_back(operacao);
    }

    input.close();

    // output the list in reverse order

    for (auto it = operations.rbegin(); it != operations.rend(); ++it)
    {
                cout << *it << endl;
     }

    return 0;
}

[Ozzy69]

But i can't use vector!

[48T7M4Gy]

But i can't use vector!

Does that mean you are not permitted or you don't understand how vectors work

If you aren't permitted to use STL containers then perhaps design and implement your own linked list?