Bubble Sort, how can I validate the numbers?

[jetter2]

So far, I have written a program that will allow me to enter the number of numbers I want in to the array, and read in the numbers. It then will use bubble sort to sequentally order them..

But I'm having a hard time doing the following;

(1) How can I validate the entered character is a number? I don't want to allow the user to enter a letter or anything other than an integer.

(2) How can I restrict the max number entries into the array to a number like 20? Right now I can enter in as many as I want, and I'm having a hard time figuring out how to restrict it.

Here's what I have so far..

#include <iostream>
using namespace std;

int compare(int, int);
void sort(int[], const int);
void swap(int *, int *);

int compare(int x, int y)
{
     return(x > y);
}

void swap(int *x, int *y)
{
     int temp;
     temp = *x;
     *x = *y;
     *y = temp;
}

void sort(int table[], const int n)
{
     for(int i = 0; i < n; i++)
     {
          for(int j = 0; j < n-1; j++)
          {
               if(compare(table[j], table[j+1]))
                    swap(&table[j], &table[j+1]);
          }
     }
}

int quantity;
int* tab;

void main()
{
cout << "Input quantity: ";
cin >> quantity;
tab = new int [quantity];
cout << "Input numbers: \n\n";
for (int i = 0; i < quantity; i++)
{
    int x = i;
    cout << "#" << ++x << ": ";
    cin >> tab[i];
}

cout << "\nBefore sorting: ";
for (int i = 0; i < quantity; i++)
{
     cout << tab[i] << " ";
}

cout << "\nAfter sorting: ";
sort(tab, quantity);
for(int i = 0; i < quantity; i++)
{
     cout << tab[i] << " ";
}

}

[Bazzy]

1) http://www.cplusplus.com/forum/articles/6046/
2)pseudocode:

if quantity > 20
    ask again // it should be a loop
else
    do what you need

[jetter2]

I'm still having some trouble with it.. I am wanting to restrict the array to a size of 20 and this is what I came up with, but my loop doesn't work..it just hangs after the first cout =[

            {
cout << "Enter the amount of numbers you would like to sort : ";
cin >> quantity;
			}

/*validate user input*/
			while(!isdigit(quantity));{
cout << "Please enter an integer : ";
cin >> quantity;}

	{

[Bazzy]

Did you read the link?

[jetter2]

I got the program running, but I still can't grasp how to verify what being entered is an integer.

#include <iostream>
using namespace std;

int compare(int, int);
void sort(int[], const int);
void swap(int *, int *);

int compare(int x, int y)
{
     return(x > y);
}

void swap(int *x, int *y)
{
     int temp;
     temp = *x;
     *x = *y;
     *y = temp;
}

void sort(int table[], const int n)
{
     for(int i = 0; i < n; i++)
     {
          for(int j = 0; j < n-1; j++)
          {
               if(compare(table[j], table[j+1]))
                    swap(&table[j], &table[j+1]);
          }
     }
}

int quantity;
int* tab;

void main()
{
cout << "Input quantity: ";
cin >> quantity;

if	(quantity > 20)
	{cout << "Enter a value less than 20 \n\n";
	cin >> quantity;
	}if	(quantity > 20)
	{cout << "Enter a value less than 20 \n\n";
	cin >> quantity;
	}if	(quantity > 20)
	{cout << "Enter a value less than 20 \n\n";
	cin >> quantity;
	}if	(quantity > 20)
	{cout << "Enter a value less than 20 \n\n";
	cin >> quantity;
	}if	(quantity > 20)
	{cout << "Enter a value less than 20 \n\n";
	cin >> quantity;
	}if	(quantity > 20)
	{cout << "Enter a value less than 20 \n\n";
	cin >> quantity;
	}if	(quantity > 20)
	{cout << "Enter a value less than 20 \n\n";
	cin >> quantity;
	}if	(quantity > 20)
	{cout << "Enter a value less than 20 \n\n";
	cin >> quantity;
	}

else (quantity <= 20);
			{cout << "Thanks \n\n";
			}



tab = new int [quantity];
cout << "Input numbers: \n\n";
for (int i = 0; i < quantity; i++)
{
    int x = i;
    cout << "#" << ++x << ": ";
    cin >> tab[i];
}

cout << "\nBefore sorting: ";
for (int i = 0; i < quantity; i++)
{
     cout << tab[i] << " ";
}

cout << "\nAfter sorting: ";
sort(tab, quantity);
for(int i = 0; i < quantity; i++)
{
     cout << tab[i] << " ";
}

}