Question

(C++) What is the best way to validate for the two user inputs in the followig for loop? Would like it to say "That value is not allowed. Enter another value." , if 1 ) numbers are not within range 2) a blank is entered 3) other characters (that are not numbers) are entered and 4) numbers with decimals or negatives are entered.

int num1;

int num2;

for(int i = 1; i <= 4; i++) {
cout << "Enter number 0-99 " << i << " ";
cin >> num1;
cout << "Enter number 1-9 " << i;
cin >> num2;
cout << endl;
}

Answer 1

// C++ code input validation
#include <iostream>
#include <string>
#include <iomanip>
#include <limits>

using namespace std;

int main ()
{

int num1 = -100;
int num2;

for (int i = 0; i < 4; ++i)
{
      cout << "Enter number 0-99 ";
      // check for numbers in range, character, special characters, negative number, decimal values
      while(!(cin >> num1) || num1 < 0 || num1 > 99)
      {
        cin.clear();
        cin.ignore(numeric_limits<streamsize>::max(), '\n');
        cout << "\nThat value is not allowed. Enter another value: ";
      }

      cout << "\n\nEnter number 1-9 ";
      // check for numbers in range, character, special characters, negative number, decimal values
      while(!(cin >> num2) || num2 < 1 || num2 > 9)
      {
        cin.clear();
        cin.ignore(numeric_limits<streamsize>::max(), '\n');
        cout << "\nThat value is not allowed. Enter another value: ";
      }

      cout << endl;

}

return 0;

}

/*
output:

Enter number 0-99 r
That value is not allowed. Enter another value: !
That value is not allowed. Enter another value: hump
That value is not allowed. Enter another value: -4
That value is not allowed. Enter another value: 109
That value is not allowed. Enter another value: 5

Enter number 1-9 g
That value is not allowed. Enter another value: !
That value is not allowed. Enter another value: -4
That value is not allowed. Enter another value: 900
That value is not allowed. Enter another value: 5

*/