Audience and Seat#

Question

Only one seat should be allocated to one audience randomly. More than one audience can't have same seat or vice versa. How can this program be completed with these conditions?

using System;

class Program
{
public static void Main()
{
int seats = 10;
int audience = 10;

int[] audArray = new int[audience];

Random r = new Random();

Console.WriteLine("{0 ,4} {1, 5}", "Audience", "Seat#");

for (int i = 1; i < audience; i++)
{
int x = r.Next(1, seats);

audArray[i] = i;

Console.WriteLine("{0, 3} {1, 6}", audArray[i], x);

}
Console.Read();
}
}

Vulpes · Answer

You need to make sure that a seat hasn't been allocated before. You can do this with the Array.IndexOf method which will return -1 if a seat number isn't already in the array. So try the following: using System; class Program { public static void Main() { int seats = 10; int audience = 10; int[] audArray = new int[audience]; // all elements zero initially Random r = new Random(); Console.WriteLine({0 4} {1 5} Audience Seat#); for (int i = 0; i { int x = r.Next(1 seats + 1); // random number between 1 and seats if(Array.IndexOf(audArray x) == -1) // seat hasn't already been used { audArray[i] = x; Console.WriteLine({0 3} {1 6} i + 1 audArray[i]); } else { i--; // need to get another random seat for index i } } Console.Read(); } }

Maha · Answer

Thank you for your explanation.

Vulpes · Answer

Before generics was introduced in .NET 2.0 the compiler would have chosen the Array.IndexOf(Array object) overload. However in later versions of .NET the generic overload Array.IndexOf (T[] T) would be considered the 'best match' for the arguments and would therefore be selected by the compiler. Incidentally the compiler uses complex rules to determine the best match but these usually result in the 'common-sense' overload being chosen. You could still force the Array.Index(Array object) overload to be chosen by changing the line to: if(Array.IndexOf(audArray (object)x) == -1) but this would be less efficient that the generic alternative as the int would need to be boxed on the heap to be accommodated by the object parameter. You could also call the generic overload with the syntax: f(Array.IndexOf (audArray x) == -1) but this is unnecessary as the compiler is able to infer the type of T from the types of the arguments.

Maha · Answer

I wish to know whether IndexOf (T[] T) was converted into non-generic by removing T and replacing with object and int . That means Array.IndexOf( object  int ).

Vulpes · Answer

The MSDN docs is as good a place as any: http://msdn.microsoft.com/en-us/library/eha9t187.aspx Notice that the overload we're using here is a generic method where T = int. The compiler infers the type of T from the fact that it's an int array and an int value that we're passing to it.

Maha · Answer

Is there any website to learn more about Array.IndexOf(object int) == -1

Maha · Answer

Thanks