I am having trouble figuring out my do-while loop. You enter a number from 1-4 and if it is correct, it'll terminate. But if !(1-4) repeat the loop again to type the number again. I have it where my else statement keeps printing an infinite loop. How do I solve the infinite loop so it can keep asking the user to enter a number?

Code:

cin >> num;
do
{
    if (num == 1 || num == 2 || num == 3 || num == 4)
    {
        cout << "Correct\n";
    }
    else
    {
        cout << "Incorrect. Try Again\n";
    }
}
while ((num != 1) && (num != 2) && (num != 3) && (num != 4));

CodePudding user response：

Your loop never updates the value of num, so if the loop enters, it can never end.

You likely wanted:

do
{
    cin >> num;
    if (num >= 1 && num <= 4)
    {
        cout << "Correct\n";
    } 
    else
    {
        cout << "Incorrect. Try Again\n";
    }
} while (num < 1 && num > 4);

Alternatively, you are checking that condition twice. You don't need to do this when you can use break to break the loop on correct input.

while (true) {
    cin >> num;
    if (num >= 1 && num <= 4) {
        cout << "Correct\n";
        break;
    }
    else {
        cout << "Incorrect. Try Again\n";
    }
}

CodePudding user response：

If you want the user to be able to enter input more than once (for example if the previous input was incorrect), then you must move the line

cin >> num;

inside the loop.

In order to prevent having the condition

num == 1 || num == 2 || num == 3 || num == 4

twice in your code (the second one is identical, except negated), it would be better to write this condition only once. Also, you can simpify it to the following:

1 <= num && num <= 4

I recommend you rewrite the loop to the following:

for (;;) //infinite loop, equivalent to while(true)
{
    cin >> num;

    if ( 1 <= num && num <= 4 )
    {
        cout << "Correct.\n";
        break;
    }

    cout << "Incorrect. Try Again.\n";
}