Remove numbers and

Question

I wrote new code and it works when the user puts 2 numbers but with more then 2 it doesn't work. I think that something has to be changed in the second for loop.



int main() {

    int N;
    cin >> N;
    vector<int>vec;
    int number;
    int firstNumber;
    cin >> firstNumber;
    vec.push_back(firstNumber);

    for (int j = 0; vec.size() < N;j++) {
        cin >> number;
        for (int i = 0; i < vec.size(); i++) {
            if (number == vec[i]) {
                cin >> number;
            }
        }
            vec.push_back(number);
    }
    for (int i = 0; i < vec.size(); i++) {
        cout << vec[i] << endl;
    }
    
    return 0;
}

https://stackoverflow.com/questions/1041620/whats-the-most-efficient-way-to-erase-duplicates-and-sort-a-vector — E. van Putten, Nov 19 '20 at 11:02
Each time a value is read, check if it is in the vector BEFORE attempting to add it to the vector. `std::find()` can help with that. — Peter, Nov 19 '20 at 11:20
@Victoria - Doesn't change the premise of checking values before adding them to the vector as distinct from (as you are) reading all values and then checking. — Peter, Nov 19 '20 at 11:28

Jabberwocky · Answer 1 · 2020-11-19T15:10:11.247

Your code is overly complicated (and obviously wrong). There is nothing special about the first number, just do all the input in the loop.

This is a way to do it, explanations in the comments:

int main() {

  int N;
  cin >> N;
  vector<int> vec;

  for (int j = 0; vec.size() < N; j++) {
    int number;                 // put variables in the closest possibel scope
    cin >> number;

    bool found = false;         // assume number is not found in the vector
    for (int i = 0; i < vec.size(); i++) {
      if (number == vec[i]) {
        found = true;           // number found
      }
    }

    if (!found)                 // don't add to vector if number has been found
      vec.push_back(number);
  }

  for (int i = 0; i < vec.size(); i++) {
    cout << vec[i] << endl;
  }

  return 0;
}

There is room for improvement:

the inner for loop can be improved (this one is easy)
you can possibly use more advanced C++ mechanisms (like std::find)
vector::size() returns a size_t not an int, therefore the for index variables and N should be size_t instead of int.

Bonus: the last loop can be simplified to this:

for (auto & value : vec) {
  cout << value << endl;
}

Remove numbers and

1 Answers1