Question

Using a 2D array for the first time for my university project.

im struggling on how to place a user entered value into a specific slot in the array.

what i do have is.

cout << "Enter Number of Groups" << endl;
cin >> DefinedGroups;

int user_groups[definedgroups] [2]

while (havent worked out the condition yet)
{
cout << " Enter Lower Range " << endl;
cin >> Lrange;
cout << " Enter Higher Range " << endl;
cin >> Hrange;
}

Anyone Know how I can enter the value from Lrange and Hrange into the array at like 0,1 and 1,1 and then increment the definedgroup by 1 each time. Thanks

Answer 1

Firstly, your code uses Variable Length Arrays which are a GCC extension. This means your code is not portable.

Now to read into the elements in the array, you could simply do:

cout << " Enter Lower Range " << endl;
cin >> user_groups[i][0];
cout << " Enter Higher Range " << endl;
cin >> user_groups[i][1];

Assuming that i is an index into the array that you’ll get when you figure out the while loop condition.

If you’d like to enlighten yourself, you could use a more idiomatic method:

int defined_groups;
std::cin >> defined_groups;
std::vector<std::pair<int, int>> user_groups;
for (int i = 0; i < defined_groups; i++) {
  int lower_range, upper_range;
  if (cout << "Enter Lower Range " << endl &&
      std::cin >> lower_range &&
      cout << " Enter Higher Range " << endl &&
      std::cin >> upper_range) {
    user_groups.push_back(std::make_pair(lower_range, upper_range));
  }
}