c++ do while loop with user input

Question

I am trying to make it so if the user enters a number less than 4 or greater them 10 they are prompted it is invalid and to enter a new number. the problem I am having is if they do enter a proper number it does not continue on to the next part. Here is what I have so far:

#include <iostream>
#include <iomanip>
#include <string>
#include <fstream>
#include <cstdlib>
#include <ctime>

int NewRandomNumber (int n);
void MakeQuestion (int n, int& a, int& b, int& atimesb);
bool UserAnswer (int a, int b, int atimesb);
void PrintScore (int numCorrect, int numAsked);

using namespace std;

int main()

{
string name;
int n;
string s;




cout << "Welcome to Multiplication Quiz 1000!" << endl;
cout << "Firstly what is your name?\n" << endl;

cin >> name;

cout << "\nHi " << name <<" !" << endl;
cout << "What difficulty would you like your quiz to be? Enter a value from [4 to 12]

      \nwith 4 being the easiest:\n" << endl;

do
{
cin >> s;
n = atoi(s.c_str());

if ( n >= 4 || n <= 10)



  if ( n < 4 || n > 10)
    {cout << "invalid. try again" << endl;
    }



{cout << "Ok" << endl;
cout << NewRandomNumber (4);
}

}
while ( n >= 4 || n <= 10);


 return 0;

 }

int NewRandomNumber (int n)

{ 

    n = rand()% 10 + 1;




return (n);

 }

void MakeQuestion (int n, int& a, int& b, int& atimesb)

{
}

use getline instead to read from the keyboard getline(cin,s); — AndersK
– AndersK, Commented Aug 15, 2013 at 12:28

Natan Streppel · Accepted Answer · 2013-08-15 12:21:41Z

4

Your while( n >= 4 || n <= 10) condition will always be true. You should go with while (n <= 4 || n >= 10).

There are a few ways to solve your problem, like it was already posted here. I would go with a continue statement, like slacker said, but be sure to change your while condition, otherwise it won`t work. It would be something like this:

while (true) {
    cin >> s;
    n = atoi(s.c_str());

    if (n <= 4 || n >= 10) {  
    // handles your exception and goes back to the beggining of the loop
    continue;
    }
    else {
    // the number was correct, so make your magic happen and then...
    break;
    }
}

edited Aug 15, 2013 at 12:21

answered Mar 19, 2013 at 4:06

Natan Streppel

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Comments

Sharun · Accepted Answer · 2013-03-19 03:50:25Z

1

I think you miss continue statement.

:

// .............

        if ( n < 4 || n > 10)
            {cout << "invalid. try again" << endl;
             continue;
            }

    //..............

answered Mar 19, 2013 at 3:50

Sharun

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Comments

DotPi · Accepted Answer · 2013-03-19 03:51:30Z

1

Try it this way by using a flag:

int flag=0;

do{

cin >> s;
n = atoi(s.c_str());


if ( n < 4 || n > 10)
{
  cout << "invalid. try again";
}
else
{
   flag=1;
   cout<<"OK"
}
}while(flag=0);

It has been quite a while since I have programmed in C++, so there may be some minor problems with syntax. But logic here should be fine.

answered Mar 19, 2013 at 3:51

DotPi

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