CODEWITHSUNDEEP
c++
William
William

Reputation: 71

How to store intergers to an array without knowing how many values are initially inputted

#include <iostream>
#include<cmath>
using namespace std;

int main(){

int grades[10];
cout << "Enter list: ";

int count = 0;
int current = 0;

while (current >= 0){
  cin >> current;
  grades[count] = current;
  count += 1;
}

cout << grades[0];

}

Should output the first int in the array but instead outputs nothing after entering a list of numbers separated by spaces (less than 10 total). Ideally, it should output the entire array but I can't figure out why it won't just output the first value of the array. I suspect it's something to do with while (current >= 0). If so then im wondering how I can check if there are no more inputs left in the stream.

Upvotes: 3

Views: 110

Answers (1)

Peter
Peter

Reputation: 36597

An array such as int grades[10] in your code cannot be resized in standard C++.

Instead, use a standard container - such as std::vector - which is designed to be resized at run time

#include <vector>
#include <iostream>

int main()
{
      std::vector<int> grades(0);     //   our container, initially sized to zero
      grades.reserve(10);             //   optional, if we can guess ten values are typical

      std::cout << "Enter list of grades separated by spaces: ";
      int input;

      while ((std::cin >> input) && input > 0)   //  exit loop on read error or input zero or less
      {
          grades.push_back(input);    // adds value to container, resizing
      }

      std::cout << grades.size() << " values have been entered\n";

      //   now we demonstrate a couple of options for outputting all the values

      for (int i = 0; i < grades.size(); ++i)   // output the values
      {
           std::cout << ' ' << grades[i];
      }
      std::cout << '\n';

      for (const auto &val : grades)   // another way to output the values (C++11 and later)
      {
           std::cout << ' ' << val;
      }
      std::cout << '\n';
}

Upvotes: 3

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